Class: Sequel::Dataset

Inherits:
Object show all
Includes:
Enumerable, SQL::AliasMethods, SQL::BooleanMethods, SQL::CastMethods, SQL::ComplexExpressionMethods, SQL::InequalityMethods, SQL::NumericMethods, SQL::OrderMethods, SQL::StringMethods
Defined in:
lib/sequel/dataset.rb,
lib/sequel/dataset/sql.rb,
lib/sequel/dataset/misc.rb,
lib/sequel/dataset/graph.rb,
lib/sequel/dataset/query.rb,
lib/sequel/dataset/actions.rb,
lib/sequel/dataset/features.rb,
lib/sequel/extensions/query.rb,
lib/sequel/extensions/pagination.rb,
lib/sequel/extensions/provenance.rb,
lib/sequel/adapters/utils/replace.rb,
lib/sequel/dataset/dataset_module.rb,
lib/sequel/extensions/null_dataset.rb,
lib/sequel/extensions/set_literalizer.rb,
lib/sequel/extensions/split_array_nil.rb,
lib/sequel/extensions/synchronize_sql.rb,
lib/sequel/dataset/prepared_statements.rb,
lib/sequel/extensions/round_timestamps.rb,
lib/sequel/extensions/implicit_subquery.rb,
lib/sequel/adapters/utils/columns_limit_1.rb,
lib/sequel/dataset/placeholder_literalizer.rb,
lib/sequel/extensions/auto_literal_strings.rb,
lib/sequel/extensions/dataset_source_alias.rb,
lib/sequel/adapters/utils/stored_procedures.rb,
lib/sequel/dataset/deprecated_singleton_class_methods.rb

Overview

A dataset represents an SQL query. Datasets can be used to select, insert, update and delete records.

Query results are always retrieved on demand, so a dataset can be kept around and reused indefinitely (datasets never cache results):

my_posts = DB[:posts].where(author: 'david') # no records are retrieved
my_posts.all # records are retrieved
my_posts.all # records are retrieved again

Datasets are frozen and use a functional style where modification methods return modified copies of the the dataset. This allows you to reuse datasets:

posts = DB[:posts]
davids_posts = posts.where(author: 'david')
old_posts = posts.where{stamp < Date.today - 7}
davids_old_posts = davids_posts.where{stamp < Date.today - 7}

Datasets are Enumerable objects, so they can be manipulated using many of the Enumerable methods, such as map and inject. Note that there are some methods that Dataset defines that override methods defined in Enumerable and result in different behavior, such as select and group_by.

For more information, see the “Dataset Basics” guide.

Defined Under Namespace

Modules: ArgumentMapper, AutoLiteralStrings, ColumnsLimit1, DatasetSourceAlias, DeprecatedSingletonClassMethods, EmulatePreparedStatementMethods, ImplicitSubquery, NullDataset, Nullifiable, Pagination, PreparedStatementMethods, Provenance, Replace, RoundTimestamps, SetLiteralizer, SplitArrayNil, StoredProcedureMethods, StoredProcedures, SynchronizeSQL, UnnumberedArgumentMapper Classes: DatasetModule, PlaceholderLiteralizer, Query

Constant Summary collapse

OPTS = 
Sequel::OPTS
TRUE_FREEZE =

Whether Dataset#freeze can actually freeze datasets. True only on ruby 2.4+, as it requires clone(freeze: false)

RUBY_VERSION >= '2.4'
WILDCARD = 
LiteralString.new('*').freeze
COUNT_OF_ALL_AS_COUNT = 
SQL::Function.new(:count, WILDCARD).as(:count)
DEFAULT = 
LiteralString.new('DEFAULT').freeze
EXISTS = 
['EXISTS '.freeze].freeze
BITWISE_METHOD_MAP = 
{:& =>:BITAND, :| => :BITOR, :^ => :BITXOR}.freeze
COUNT_FROM_SELF_OPTS = 
[:distinct, :group, :sql, :limit, :offset, :compounds].freeze
IS_LITERALS = 
{nil=>'NULL'.freeze, true=>'TRUE'.freeze, false=>'FALSE'.freeze}.freeze
QUALIFY_KEYS = 
[:select, :where, :having, :order, :group].freeze
IS_OPERATORS = 
::Sequel::SQL::ComplexExpression::IS_OPERATORS
LIKE_OPERATORS = 
::Sequel::SQL::ComplexExpression::LIKE_OPERATORS
N_ARITY_OPERATORS = 
::Sequel::SQL::ComplexExpression::N_ARITY_OPERATORS
TWO_ARITY_OPERATORS = 
::Sequel::SQL::ComplexExpression::TWO_ARITY_OPERATORS
REGEXP_OPERATORS = 
::Sequel::SQL::ComplexExpression::REGEXP_OPERATORS
EXTENSIONS =

Hash of extension name symbols to callable objects to load the extension into the Dataset object (usually by extending it with a module defined in the extension).

{}
EMPTY_ARRAY = 
[].freeze
COLUMN_CHANGE_OPTS =

The dataset options that require the removal of cached columns if changed.

[:select, :sql, :from, :join].freeze
NON_SQL_OPTIONS =

Which options don’t affect the SQL generation. Used by simple_select_all? to determine if this is a simple SELECT * FROM table.

[:server, :graph, :row_proc, :quote_identifiers, :skip_symbol_cache].freeze
CONDITIONED_JOIN_TYPES =

These symbols have _join methods created (e.g. inner_join) that call join_table with the symbol, passing along the arguments and block from the method call.

[:inner, :full_outer, :right_outer, :left_outer, :full, :right, :left].freeze
UNCONDITIONED_JOIN_TYPES =

These symbols have _join methods created (e.g. natural_join). They accept a table argument and options hash which is passed to join_table, and they raise an error if called with a block.

[:natural, :natural_left, :natural_right, :natural_full, :cross].freeze
JOIN_METHODS =

All methods that return modified datasets with a joined table added.

((CONDITIONED_JOIN_TYPES + UNCONDITIONED_JOIN_TYPES).map{|x| "#{x}_join".to_sym} + [:join, :join_table]).freeze
QUERY_METHODS =

Methods that return modified datasets

((<<-METHS).split.map(&:to_sym) + JOIN_METHODS).freeze
  add_graph_aliases distinct except exclude exclude_having
  filter for_update from from_self graph grep group group_and_count group_append group_by having intersect invert
  limit lock_style naked offset or order order_append order_by order_more order_prepend qualify
  reverse reverse_order select select_all select_append select_group select_more select_prepend server
  set_graph_aliases unfiltered ungraphed ungrouped union
  unlimited unordered where with with_recursive with_sql
METHS
ACTION_METHODS =

Action methods defined by Sequel that execute code on the database.

(<<-METHS).split.map(&:to_sym).freeze
  << [] all as_hash avg count columns columns! delete each
  empty? fetch_rows first first! get import insert last
  map max min multi_insert paged_each select_hash select_hash_groups select_map select_order_map
  single_record single_record! single_value single_value! sum to_hash to_hash_groups truncate update
  where_all where_each where_single_value
METHS
COLUMNS_CLONE_OPTIONS =

The clone options to use when retrieving columns for a dataset.

{:distinct => nil, :limit => 0, :offset=>nil, :where=>nil, :having=>nil, :order=>nil, :row_proc=>nil, :graph=>nil, :eager_graph=>nil}.freeze
COUNT_SELECT = 
Sequel.function(:count).*.as(:count)
EMPTY_SELECT = 
Sequel::SQL::AliasedExpression.new(1, :one)
PREPARED_ARG_PLACEHOLDER =

:section: 8 - Methods related to prepared statements or bound variables On some adapters, these use native prepared statements and bound variables, on others support is emulated. For details, see the “Prepared Statements/Bound Variables” guide.

LiteralString.new('?').freeze
DEFAULT_PREPARED_STATEMENT_MODULE_METHODS = 
%w'execute execute_dui execute_insert'.freeze.each(&:freeze)
PREPARED_STATEMENT_MODULE_CODE = 
{
  :bind => "opts = Hash[opts]; opts[:arguments] = bind_arguments".freeze,
  :prepare => "sql = prepared_statement_name".freeze,
  :prepare_bind => "sql = prepared_statement_name; opts = Hash[opts]; opts[:arguments] = bind_arguments".freeze
}.freeze

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods included from SQL::StringMethods

#escaped_ilike, #escaped_like, #ilike, #like

Methods included from SQL::OrderMethods

#asc, #desc

Methods included from SQL::NumericMethods

#+, #coerce

Methods included from SQL::ComplexExpressionMethods

#extract, #sql_boolean, #sql_number, #sql_string

Methods included from SQL::CastMethods

#cast, #cast_numeric, #cast_string

Methods included from SQL::BooleanMethods

#~

Methods included from SQL::AliasMethods

#as

Constructor Details

#initialize(db) ⇒ Dataset

Constructs a new Dataset instance with an associated database and options. Datasets are usually constructed by invoking the Database#[] method:

DB[:posts]

Sequel::Dataset is an abstract class that is not useful by itself. Each database adapter provides a subclass of Sequel::Dataset, and has the Database#dataset method return an instance of that subclass.



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# File 'lib/sequel/dataset/misc.rb', line 25

def initialize(db)
  @db = db
  @opts = OPTS
  @cache = {}
  freeze
end

Instance Attribute Details

#db ⇒ Object (readonly)

The database related to this dataset. This is the Database instance that will execute all of this dataset’s queries.



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# File 'lib/sequel/dataset/misc.rb', line 12

def db
  @db
end

#opts ⇒ Object (readonly)

The hash of options for this dataset, keys are symbols.



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# File 'lib/sequel/dataset/misc.rb', line 15

def opts
  @opts
end

Class Method Details

.clause_methods(type, clauses) ⇒ Object

Given a type (e.g. select) and an array of clauses, return an array of methods to call to build the SQL string.



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# File 'lib/sequel/dataset/sql.rb', line 225

def self.clause_methods(type, clauses)
  clauses.map{|clause| :"#{type}_#{clause}_sql"}.freeze
end

.def_sql_method(mod, type, clauses) ⇒ Object

Define a dataset literalization method for the given type in the given module, using the given clauses.

Arguments:

mod

Module in which to define method

type

Type of SQL literalization method to create, either :select, :insert, :update, or :delete

clauses

array of clauses that make up the SQL query for the type. This can either be a single array of symbols/strings, or it can be an array of pairs, with the first element in each pair being an if/elsif/else code fragment, and the second element in each pair being an array of symbol/strings for the appropriate branch.



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# File 'lib/sequel/dataset/sql.rb', line 239

def self.def_sql_method(mod, type, clauses)
  priv = type == :update || type == :insert
  cacheable = type == :select || type == :delete

  lines = []
  lines << 'private' if priv
  lines << "def #{'_' if priv}#{type}_sql"
  lines << 'if sql = opts[:sql]; return static_sql(sql) end' unless priv
  lines << "if sql = cache_get(:_#{type}_sql); return sql end" if cacheable
  lines << 'check_delete_allowed!' << 'check_not_limited!(:delete)' if type == :delete
  lines << 'sql = @opts[:append_sql] || sql_string_origin'

  if clauses.all?{|c| c.is_a?(Array)}
    clauses.each do |i, cs|
      lines << i
      lines.concat(clause_methods(type, cs).map{|x| "#{x}(sql)"}) 
    end 
    lines << 'end'
  else
    lines.concat(clause_methods(type, clauses).map{|x| "#{x}(sql)"})
  end

  lines << "cache_set(:_#{type}_sql, sql) if cache_sql?" if cacheable
  lines << 'sql'
  lines << 'end'

  mod.class_eval lines.join("\n"), __FILE__, __LINE__
end

.register_extension(ext, mod = nil, &block) ⇒ Object

Register an extension callback for Dataset objects. ext should be the extension name symbol, and mod should be a Module that will be included in the dataset’s class. This also registers a Database extension that will extend all of the database’s datasets.



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# File 'lib/sequel/dataset/query.rb', line 55

def self.register_extension(ext, mod=nil, &block)
  if mod
    raise(Error, "cannot provide both mod and block to Dataset.register_extension") if block
    if mod.is_a?(Module)
      block = proc{|ds| ds.extend(mod)}
      Sequel::Database.register_extension(ext){|db| db.extend_datasets(mod)}
      Sequel.synchronize{EXTENSION_MODULES[ext] = mod}
    else
      block = mod
    end
  end

  unless mod.is_a?(Module)
    Sequel::Deprecation.deprecate("Providing a block or non-module to Sequel::Dataset.register_extension is deprecated and support for it will be removed in Sequel 6.")
  end

  Sequel.synchronize{EXTENSIONS[ext] = block}
end

Instance Method Details

#<<(arg) ⇒ Object

Inserts the given argument into the database. Returns self so it can be used safely when chaining:

DB[:items] << {id: 0, name: 'Zero'} << DB[:old_items].select(:id, name)



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# File 'lib/sequel/dataset/actions.rb', line 28

def <<(arg)
  insert(arg)
  self
end

#==(o) ⇒ Object

Define a hash value such that datasets with the same class, DB, and opts will be considered equal.



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# File 'lib/sequel/dataset/misc.rb', line 34

def ==(o)
  o.is_a?(self.class) && db == o.db && opts == o.opts
end

#[](*conditions) ⇒ Object

Returns the first record matching the conditions. Examples:

DB[:table][id: 1] # SELECT * FROM table WHERE (id = 1) LIMIT 1
# => {:id=>1}

Raises:



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# File 'lib/sequel/dataset/actions.rb', line 37

def [](*conditions)
  raise(Error, 'You cannot call Dataset#[] with an integer or with no arguments') if (conditions.length == 1 and conditions.first.is_a?(Integer)) or conditions.length == 0
  first(*conditions)
end

#add_graph_aliases(graph_aliases) ⇒ Object

Adds the given graph aliases to the list of graph aliases to use, unlike set_graph_aliases, which replaces the list (the equivalent of select_append when graphing). See set_graph_aliases.

DB[:table].add_graph_aliases(some_alias: [:table, :column])
# SELECT ..., table.column AS some_alias



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# File 'lib/sequel/dataset/graph.rb', line 18

def add_graph_aliases(graph_aliases)
  graph = opts[:graph]
  unless (graph && (ga = graph[:column_aliases]))
    raise Error, "cannot call add_graph_aliases on a dataset that has not been called with graph or set_graph_aliases"
  end
  columns, graph_aliases = graph_alias_columns(graph_aliases)
  select_append(*columns).clone(:graph => graph.merge(:column_aliases=>ga.merge(graph_aliases).freeze).freeze)
end

#aliased_expression_sql_append(sql, ae) ⇒ Object

Append literalization of aliased expression to SQL string.



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# File 'lib/sequel/dataset/sql.rb', line 300

def aliased_expression_sql_append(sql, ae)
  literal_append(sql, ae.expression)
  as_sql_append(sql, ae.alias, ae.columns)
end

#all(&block) ⇒ Object

Returns an array with all records in the dataset. If a block is given, the array is iterated over after all items have been loaded.

DB[:table].all # SELECT * FROM table
# => [{:id=>1, ...}, {:id=>2, ...}, ...]

# Iterate over all rows in the table
DB[:table].all{|row| p row}



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# File 'lib/sequel/dataset/actions.rb', line 50

def all(&block)
  _all(block){|a| each{|r| a << r}}
end

#array_sql_append(sql, a) ⇒ Object

Append literalization of array to SQL string.



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# File 'lib/sequel/dataset/sql.rb', line 306

def array_sql_append(sql, a)
  if a.empty?
    sql << '(NULL)'
  else
    sql << '('
    expression_list_append(sql, a)
    sql << ')'
  end
end

#as_hash(key_column, value_column = nil, opts = OPTS) ⇒ Object

Returns a hash with one column used as key and another used as value. If rows have duplicate values for the key column, the latter row(s) will overwrite the value of the previous row(s). If the value_column is not given or nil, uses the entire hash as the value.

DB[:table].as_hash(:id, :name) # SELECT * FROM table
# {1=>'Jim', 2=>'Bob', ...}

DB[:table].as_hash(:id) # SELECT * FROM table
# {1=>{:id=>1, :name=>'Jim'}, 2=>{:id=>2, :name=>'Bob'}, ...}

You can also provide an array of column names for either the key_column, the value column, or both:

DB[:table].as_hash([:id, :foo], [:name, :bar]) # SELECT * FROM table
# {[1, 3]=>['Jim', 'bo'], [2, 4]=>['Bob', 'be'], ...}

DB[:table].as_hash([:id, :name]) # SELECT * FROM table
# {[1, 'Jim']=>{:id=>1, :name=>'Jim'}, [2, 'Bob']=>{:id=>2, :name=>'Bob'}, ...}

Options:

:all

Use all instead of each to retrieve the objects

:hash

The object into which the values will be placed. If this is not given, an empty hash is used. This can be used to use a hash with a default value or default proc.



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# File 'lib/sequel/dataset/actions.rb', line 855

def as_hash(key_column, value_column = nil, opts = OPTS)
  h = opts[:hash] || {}
  meth = opts[:all] ? :all : :each
  if value_column
    return naked.as_hash(key_column, value_column, opts) if row_proc
    if value_column.is_a?(Array)
      if key_column.is_a?(Array)
        public_send(meth){|r| h[r.values_at(*key_column)] = r.values_at(*value_column)}
      else
        public_send(meth){|r| h[r[key_column]] = r.values_at(*value_column)}
      end
    else
      if key_column.is_a?(Array)
        public_send(meth){|r| h[r.values_at(*key_column)] = r[value_column]}
      else
        public_send(meth){|r| h[r[key_column]] = r[value_column]}
      end
    end
  elsif key_column.is_a?(Array)
    public_send(meth){|r| h[key_column.map{|k| r[k]}] = r}
  else
    public_send(meth){|r| h[r[key_column]] = r}
  end
  h
end

#avg(arg = (no_arg = true), &block) ⇒ Object

Returns the average value for the given column/expression. Uses a virtual row block if no argument is given.

DB[:table].avg(:number) # SELECT avg(number) FROM table LIMIT 1
# => 3
DB[:table].avg{function(column)} # SELECT avg(function(column)) FROM table LIMIT 1
# => 1



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# File 'lib/sequel/dataset/actions.rb', line 61

def avg(arg=(no_arg = true), &block)
  arg = Sequel.virtual_row(&block) if no_arg
  _aggregate(:avg, arg)
end

#bind(bind_vars = OPTS) ⇒ Object

Set the bind variables to use for the call. If bind variables have already been set for this dataset, they are updated with the contents of bind_vars.

DB[:table].where(id: :$id).bind(id: 1).call(:first)
# SELECT * FROM table WHERE id = ? LIMIT 1 -- (1)
# => {:id=>1}



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# File 'lib/sequel/dataset/prepared_statements.rb', line 332

def bind(bind_vars=OPTS)
  bind_vars = if bv = @opts[:bind_vars]
    bv.merge(bind_vars).freeze
  else
    if bind_vars.frozen?
      bind_vars
    else
      Hash[bind_vars]
    end
  end

  clone(:bind_vars=>bind_vars)
end

#boolean_constant_sql_append(sql, constant) ⇒ Object

Append literalization of boolean constant to SQL string.



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# File 'lib/sequel/dataset/sql.rb', line 317

def boolean_constant_sql_append(sql, constant)
  if (constant == true || constant == false) && !supports_where_true?
    sql << (constant == true ? '(1 = 1)' : '(1 = 0)')
  else
    literal_append(sql, constant)
  end
end

#call(type, bind_variables = OPTS, *values, &block) ⇒ Object

For the given type (:select, :first, :insert, :insert_select, :update, :delete, or :single_value), run the sql with the bind variables specified in the hash. values is a hash passed to insert or update (if one of those types is used), which may contain placeholders.

DB[:table].where(id: :$id).call(:first, id: 1)
# SELECT * FROM table WHERE id = ? LIMIT 1 -- (1)
# => {:id=>1}



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# File 'lib/sequel/dataset/prepared_statements.rb', line 353

def call(type, bind_variables=OPTS, *values, &block)
  to_prepared_statement(type, values, :extend=>bound_variable_modules).call(bind_variables, &block)
end

#case_expression_sql_append(sql, ce) ⇒ Object

Append literalization of case expression to SQL string.



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# File 'lib/sequel/dataset/sql.rb', line 326

def case_expression_sql_append(sql, ce)
  sql << '(CASE'
  if ce.expression?
    sql << ' '
    literal_append(sql, ce.expression)
  end
  w = " WHEN "
  t = " THEN "
  ce.conditions.each do |c,r|
    sql << w
    literal_append(sql, c)
    sql << t
    literal_append(sql, r)
  end
  sql << " ELSE "
  literal_append(sql, ce.default)
  sql << " END)"
end

#cast_sql_append(sql, expr, type) ⇒ Object

Append literalization of cast expression to SQL string.



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# File 'lib/sequel/dataset/sql.rb', line 346

def cast_sql_append(sql, expr, type)
  sql << 'CAST('
  literal_append(sql, expr)
  sql << ' AS ' << db.cast_type_literal(type).to_s
  sql << ')'
end

#clone(opts = OPTS) ⇒ Object

:nocov:



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# File 'lib/sequel/dataset/query.rb', line 90

def clone(opts = nil || (return self))
  # return self used above because clone is called by almost all
  # other query methods, and it is the fastest approach
  c = super(:freeze=>false)
  c.opts.merge!(opts)
  unless opts.each_key{|o| break if COLUMN_CHANGE_OPTS.include?(o)}
    c.clear_columns_cache
  end
  c.freeze
end

#column_all_sql_append(sql, ca) ⇒ Object

Append literalization of column all selection to SQL string.



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# File 'lib/sequel/dataset/sql.rb', line 354

def column_all_sql_append(sql, ca)
  qualified_identifier_sql_append(sql, ca.table, WILDCARD)
end

#columns ⇒ Object

Returns the columns in the result set in order as an array of symbols. If the columns are currently cached, returns the cached value. Otherwise, a SELECT query is performed to retrieve a single row in order to get the columns.

If you are looking for all columns for a single table and maybe some information about each column (e.g. database type), see Database#schema.

DB[:table].columns
# => [:id, :name]



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# File 'lib/sequel/dataset/actions.rb', line 75

def columns
  _columns || columns!
end

#columns! ⇒ Object

Ignore any cached column information and perform a query to retrieve a row in order to get the columns.

DB[:table].columns!
# => [:id, :name]



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# File 'lib/sequel/dataset/actions.rb', line 84

def columns!
  ds = clone(COLUMNS_CLONE_OPTIONS)
  ds.each{break}

  if cols = ds.cache[:_columns]
    self.columns = cols
  else
    []
  end
end

#complex_expression_sql_append(sql, op, args) ⇒ Object

Append literalization of complex expression to SQL string.



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# File 'lib/sequel/dataset/sql.rb', line 359

def complex_expression_sql_append(sql, op, args)
  case op
  when *IS_OPERATORS
    r = args[1]
    if r.nil? || supports_is_true?
      raise(InvalidOperation, 'Invalid argument used for IS operator') unless val = IS_LITERALS[r]
      sql << '('
      literal_append(sql, args[0])
      sql << ' ' << op.to_s << ' '
      sql << val << ')'
    elsif op == :IS
      complex_expression_sql_append(sql, :"=", args)
    else
      complex_expression_sql_append(sql, :OR, [SQL::BooleanExpression.new(:"!=", *args), SQL::BooleanExpression.new(:IS, args[0], nil)])
    end
  when :IN, :"NOT IN"
    cols = args[0]
    vals = args[1]
    col_array = true if cols.is_a?(Array)
    if vals.is_a?(Array)
      val_array = true
      empty_val_array = vals == []
    end
    if empty_val_array
      literal_append(sql, empty_array_value(op, cols))
    elsif col_array
      if !supports_multiple_column_in?
        if val_array
          expr = SQL::BooleanExpression.new(:OR, *vals.to_a.map{|vs| SQL::BooleanExpression.from_value_pairs(cols.to_a.zip(vs).map{|c, v| [c, v]})})
          literal_append(sql, op == :IN ? expr : ~expr)
        else
          old_vals = vals
          vals = vals.naked if vals.is_a?(Sequel::Dataset)
          vals = vals.to_a
          val_cols = old_vals.columns
          complex_expression_sql_append(sql, op, [cols, vals.map!{|x| x.values_at(*val_cols)}])
        end
      else
        # If the columns and values are both arrays, use array_sql instead of
        # literal so that if values is an array of two element arrays, it
        # will be treated as a value list instead of a condition specifier.
        sql << '('
        literal_append(sql, cols)
        sql << ' ' << op.to_s << ' '
        if val_array
          array_sql_append(sql, vals)
        else
          literal_append(sql, vals)
        end
        sql << ')'
      end
    else
      sql << '('
      literal_append(sql, cols)
      sql << ' ' << op.to_s << ' '
      literal_append(sql, vals)
      sql << ')'
    end
  when :LIKE, :'NOT LIKE'
    sql << '('
    literal_append(sql, args[0])
    sql << ' ' << op.to_s << ' '
    literal_append(sql, args[1])
    if requires_like_escape?
      sql << " ESCAPE "
      literal_append(sql, "\\")
    end
    sql << ')'
  when :ILIKE, :'NOT ILIKE'
    complex_expression_sql_append(sql, (op == :ILIKE ? :LIKE : :"NOT LIKE"), args.map{|v| Sequel.function(:UPPER, v)})
  when :**
    function_sql_append(sql, Sequel.function(:power, *args))
  when *TWO_ARITY_OPERATORS
    if REGEXP_OPERATORS.include?(op) && !supports_regexp?
      raise InvalidOperation, "Pattern matching via regular expressions is not supported on #{db.database_type}"
    end
    sql << '('
    literal_append(sql, args[0])
    sql << ' ' << op.to_s << ' '
    literal_append(sql, args[1])
    sql << ')'
  when *N_ARITY_OPERATORS
    sql << '('
    c = false
    op_str = " #{op} "
    args.each do |a|
      sql << op_str if c
      literal_append(sql, a)
      c ||= true
    end
    sql << ')'
  when :NOT
    sql << 'NOT '
    literal_append(sql, args[0])
  when :NOOP
    literal_append(sql, args[0])
  when :'B~'
    sql << '~'
    literal_append(sql, args[0])
  when :extract
    sql << 'extract(' << args[0].to_s << ' FROM '
    literal_append(sql, args[1])
    sql << ')'
  else
    raise(InvalidOperation, "invalid operator #{op}")
  end
end

#constant_sql_append(sql, constant) ⇒ Object

Append literalization of constant to SQL string.



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# File 'lib/sequel/dataset/sql.rb', line 468

def constant_sql_append(sql, constant)
  sql << constant.to_s
end

#count(arg = (no_arg=true), &block) ⇒ Object

Returns the number of records in the dataset. If an argument is provided, it is used as the argument to count. If a block is provided, it is treated as a virtual row, and the result is used as the argument to count.

DB[:table].count # SELECT count(*) AS count FROM table LIMIT 1
# => 3
DB[:table].count(:column) # SELECT count(column) AS count FROM table LIMIT 1
# => 2
DB[:table].count{foo(column)} # SELECT count(foo(column)) AS count FROM table LIMIT 1
# => 1



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# File 'lib/sequel/dataset/actions.rb', line 108

def count(arg=(no_arg=true), &block)
  if no_arg && !block
    cached_dataset(:_count_ds) do
      aggregate_dataset.select(COUNT_SELECT).single_value_ds
    end.single_value!.to_i
  else
    if block
      if no_arg
        arg = Sequel.virtual_row(&block)
      else
        raise Error, 'cannot provide both argument and block to Dataset#count'
      end
    end

    _aggregate(:count, arg)
  end
end

#current_datetime ⇒ Object

An object representing the current date or time, should be an instance of Sequel.datetime_class.



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# File 'lib/sequel/dataset/misc.rb', line 40

def current_datetime
  Sequel.datetime_class.now
end

#delayed_evaluation_sql_append(sql, delay) ⇒ Object

Append literalization of delayed evaluation to SQL string, causing the delayed evaluation proc to be evaluated.



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# File 'lib/sequel/dataset/sql.rb', line 474

def delayed_evaluation_sql_append(sql, delay)
  # Delayed evaluations are used specifically so the SQL
  # can differ in subsequent calls, so we definitely don't
  # want to cache the sql in this case.
  disable_sql_caching!

  if recorder = @opts[:placeholder_literalizer]
    recorder.use(sql, lambda{delay.call(self)}, nil)
  else
    literal_append(sql, delay.call(self))
  end
end

#delete(&block) ⇒ Object

Deletes the records in the dataset, returning the number of records deleted.

DB[:table].delete # DELETE * FROM table
# => 3

Some databases support using multiple tables in a DELETE query. This requires multiple FROM tables (JOINs can also be used). As multiple FROM tables use an implicit CROSS JOIN, you should make sure your WHERE condition uses the appropriate filters for the FROM tables:

DB.from(:a, :b).join(:c, :d=>Sequel[:b][:e]).where{{a[:f]=>b[:g], a[:id]=>c[:h]}}.
  delete
# DELETE FROM a
# USING b
# INNER JOIN c ON (c.d = b.e)
# WHERE ((a.f = b.g) AND (a.id = c.h))



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# File 'lib/sequel/dataset/actions.rb', line 142

def delete(&block)
  sql = delete_sql
  if uses_returning?(:delete)
    returning_fetch_rows(sql, &block)
  else
    execute_dui(sql)
  end
end

#distinct(*args, &block) ⇒ Object

Returns a copy of the dataset with the SQL DISTINCT clause. The DISTINCT clause is used to remove duplicate rows from the output. If arguments are provided, uses a DISTINCT ON clause, in which case it will only be distinct on those columns, instead of all returned columns. If a block is given, it is treated as a virtual row block, similar to where. Raises an error if arguments are given and DISTINCT ON is not supported.

DB[:items].distinct # SQL: SELECT DISTINCT * FROM items
DB[:items].order(:id).distinct(:id) # SQL: SELECT DISTINCT ON (id) * FROM items ORDER BY id
DB[:items].order(:id).distinct{func(:id)} # SQL: SELECT DISTINCT ON (func(id)) * FROM items ORDER BY id

There is support for emulating the DISTINCT ON support in MySQL, but it does not support the ORDER of the dataset, and also doesn’t work in many cases if the ONLY_FULL_GROUP_BY sql_mode is used, which is the default on MySQL 5.7.5+.



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# File 'lib/sequel/dataset/query.rb', line 129

def distinct(*args, &block)
  virtual_row_columns(args, block)
  if args.empty?
    return self if opts[:distinct] == EMPTY_ARRAY
    cached_dataset(:_distinct_ds){clone(:distinct => EMPTY_ARRAY)}
  else
    raise(InvalidOperation, "DISTINCT ON not supported") unless supports_distinct_on?
    clone(:distinct => args.freeze)
  end
end

#dup ⇒ Object

Return self, as datasets are always frozen.



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# File 'lib/sequel/dataset/misc.rb', line 50

def dup
  self
end

#each ⇒ Object

Iterates over the records in the dataset as they are yielded from the database adapter, and returns self.

DB[:table].each{|row| p row} # SELECT * FROM table

Note that this method is not safe to use on many adapters if you are running additional queries inside the provided block. If you are running queries inside the block, you should use all instead of each for the outer queries, or use a separate thread or shard inside each.



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# File 'lib/sequel/dataset/actions.rb', line 160

def each
  if rp = row_proc
    fetch_rows(select_sql){|r| yield rp.call(r)}
  else
    fetch_rows(select_sql){|r| yield r}
  end
  self
end

#each_server ⇒ Object

Yield a dataset for each server in the connection pool that is tied to that server. Intended for use in sharded environments where all servers need to be modified with the same data:

DB[:configs].where(key: 'setting').each_server{|ds| ds.update(value: 'new_value')}



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# File 'lib/sequel/dataset/misc.rb', line 59

def each_server
  db.servers.each{|s| yield server(s)}
end

#empty? ⇒ Boolean

Returns true if no records exist in the dataset, false otherwise

DB[:table].empty? # SELECT 1 AS one FROM table LIMIT 1
# => false

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/actions.rb', line 175

def empty?
  cached_dataset(:_empty_ds) do
    (@opts[:sql] ? from_self : self).single_value_ds.unordered.select(EMPTY_SELECT)
  end.single_value!.nil?
end

#eql?(o) ⇒ Boolean

Alias for ==

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/misc.rb', line 45

def eql?(o)
  self == o
end

#escape_like(string) ⇒ Object

Returns the string with the LIKE metacharacters (% and _) escaped. Useful for when the LIKE term is a user-provided string where metacharacters should not be recognized. Example:

ds.escape_like("foo\\%_") # 'foo\\\%\_'



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# File 'lib/sequel/dataset/misc.rb', line 68

def escape_like(string)
  string.gsub(/[\\%_]/){|m| "\\#{m}"}
end

#except(dataset, opts = OPTS) ⇒ Object

Adds an EXCEPT clause using a second dataset object. An EXCEPT compound dataset returns all rows in the current dataset that are not in the given dataset. Raises an InvalidOperation if the operation is not supported. Options:

:alias

Use the given value as the from_self alias

:all

Set to true to use EXCEPT ALL instead of EXCEPT, so duplicate rows can occur

:from_self

Set to false to not wrap the returned dataset in a from_self, use with care.

DB[:items].except(DB[:other_items])
# SELECT * FROM (SELECT * FROM items EXCEPT SELECT * FROM other_items) AS t1

DB[:items].except(DB[:other_items], all: true, from_self: false)
# SELECT * FROM items EXCEPT ALL SELECT * FROM other_items

DB[:items].except(DB[:other_items], alias: :i)
# SELECT * FROM (SELECT * FROM items EXCEPT SELECT * FROM other_items) AS i

Raises:

  • (InvalidOperation) 


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# File 'lib/sequel/dataset/query.rb', line 157

def except(dataset, opts=OPTS)
  raise(InvalidOperation, "EXCEPT not supported") unless supports_intersect_except?
  raise(InvalidOperation, "EXCEPT ALL not supported") if opts[:all] && !supports_intersect_except_all?
  compound_clone(:except, dataset, opts)
end

#exclude(*cond, &block) ⇒ Object

Performs the inverse of Dataset#where. Note that if you have multiple filter conditions, this is not the same as a negation of all conditions.

DB[:items].exclude(category: 'software')
# SELECT * FROM items WHERE (category != 'software')

DB[:items].exclude(category: 'software', id: 3)
# SELECT * FROM items WHERE ((category != 'software') OR (id != 3))

Also note that SQL uses 3-valued boolean logic (true, false, NULL), so the inverse of a true condition is a false condition, and will still not match rows that were NULL originally. If you take the earlier example:

DB[:items].exclude(category: 'software')
# SELECT * FROM items WHERE (category != 'software')

Note that this does not match rows where category is NULL. This is because NULL is an unknown value, and you do not know whether or not the NULL category is software. You can explicitly specify how to handle NULL values if you want:

DB[:items].exclude(Sequel.~(category: nil) & {category: 'software'})
# SELECT * FROM items WHERE ((category IS NULL) OR (category != 'software'))



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# File 'lib/sequel/dataset/query.rb', line 187

def exclude(*cond, &block)
  add_filter(:where, cond, true, &block)
end

#exclude_having(*cond, &block) ⇒ Object

Inverts the given conditions and adds them to the HAVING clause.

DB[:items].select_group(:name).exclude_having{count(name) < 2}
# SELECT name FROM items GROUP BY name HAVING (count(name) >= 2)

See documentation for exclude for how inversion is handled in regards to SQL 3-valued boolean logic.



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# File 'lib/sequel/dataset/query.rb', line 198

def exclude_having(*cond, &block)
  add_filter(:having, cond, true, &block)
end

#exists ⇒ Object

Returns an EXISTS clause for the dataset as an SQL::PlaceholderLiteralString.

DB.select(1).where(DB[:items].exists)
# SELECT 1 WHERE (EXISTS (SELECT * FROM items))



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# File 'lib/sequel/dataset/sql.rb', line 14

def exists
  SQL::PlaceholderLiteralString.new(EXISTS, [self], true)
end

#extension(*exts) ⇒ Object

:nocov:



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# File 'lib/sequel/dataset/query.rb', line 206

def extension(*exts)
  Sequel.extension(*exts)
  mods = exts.map{|ext| Sequel.synchronize{EXTENSION_MODULES[ext]}}
  if mods.all?
    with_extend(*mods)
  else
    with_extend(DeprecatedSingletonClassMethods).extension(*exts)
  end
end

#filter(*cond, &block) ⇒ Object

Alias for where.



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# File 'lib/sequel/dataset/query.rb', line 226

def filter(*cond, &block)
  where(*cond, &block)
end

#first(*args, &block) ⇒ Object

Returns the first matching record if no arguments are given. If a integer argument is given, it is interpreted as a limit, and then returns all matching records up to that limit. If any other type of argument(s) is passed, it is treated as a filter and the first matching record is returned. If a block is given, it is used to filter the dataset before returning anything.

If there are no records in the dataset, returns nil (or an empty array if an integer argument is given).

Examples:

DB[:table].first # SELECT * FROM table LIMIT 1
# => {:id=>7}

DB[:table].first(2) # SELECT * FROM table LIMIT 2
# => [{:id=>6}, {:id=>4}]

DB[:table].first(id: 2) # SELECT * FROM table WHERE (id = 2) LIMIT 1
# => {:id=>2}

DB[:table].first(Sequel.lit("id = 3")) # SELECT * FROM table WHERE (id = 3) LIMIT 1
# => {:id=>3}

DB[:table].first(Sequel.lit("id = ?", 4)) # SELECT * FROM table WHERE (id = 4) LIMIT 1
# => {:id=>4}

DB[:table].first{id > 2} # SELECT * FROM table WHERE (id > 2) LIMIT 1
# => {:id=>5}

DB[:table].first(Sequel.lit("id > ?", 4)){id < 6} # SELECT * FROM table WHERE ((id > 4) AND (id < 6)) LIMIT 1
# => {:id=>5}

DB[:table].first(2){id < 2} # SELECT * FROM table WHERE (id < 2) LIMIT 2
# => [{:id=>1}]



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# File 'lib/sequel/dataset/actions.rb', line 216

def first(*args, &block)
  case args.length
  when 0
    unless block
      return(@opts[:sql] ? single_record! : single_record)
    end
  when 1
    arg = args[0]
    if arg.is_a?(Integer)
      res = if block
        if loader = cached_placeholder_literalizer(:_first_integer_cond_loader) do |pl|
            where(pl.arg).limit(pl.arg)
          end

          loader.all(filter_expr(&block), arg)
        else
          where(&block).limit(arg).all
        end
      else
        if loader = cached_placeholder_literalizer(:_first_integer_loader) do |pl|
           limit(pl.arg)
          end

          loader.all(arg)
        else
          limit(arg).all
        end
      end

      return res
    end
    where_args = args
    args = arg
  end

  if loader = cached_where_placeholder_literalizer(where_args||args, block, :_first_cond_loader) do |pl|
      _single_record_ds.where(pl.arg)
    end

    loader.first(filter_expr(args, &block))
  else
    _single_record_ds.where(args, &block).single_record!
  end
end

#first!(*args, &block) ⇒ Object

Calls first. If first returns nil (signaling that no row matches), raise a Sequel::NoMatchingRow exception.



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# File 'lib/sequel/dataset/actions.rb', line 263

def first!(*args, &block)
  first(*args, &block) || raise(Sequel::NoMatchingRow.new(self))
end

#first_source ⇒ Object

Alias of first_source_alias



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# File 'lib/sequel/dataset/misc.rb', line 91

def first_source
  first_source_alias
end

#first_source_alias ⇒ Object

The first source (primary table) for this dataset. If the dataset doesn’t have a table, raises an Error. If the table is aliased, returns the aliased name.

DB[:table].first_source_alias
# => :table

DB[Sequel[:table].as(:t)].first_source_alias
# => :t



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# File 'lib/sequel/dataset/misc.rb', line 103

def first_source_alias
  source = @opts[:from]
  if source.nil? || source.empty?
    raise Error, 'No source specified for query'
  end
  case s = source.first
  when SQL::AliasedExpression
    s.alias
  when Symbol
    _, _, aliaz = split_symbol(s)
    aliaz ? aliaz.to_sym : s
  else
    s
  end
end

#first_source_table ⇒ Object

The first source (primary table) for this dataset. If the dataset doesn’t have a table, raises an error. If the table is aliased, returns the original table, not the alias

DB[:table].first_source_table
# => :table

DB[Sequel[:table].as(:t)].first_source_table
# => :table



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# File 'lib/sequel/dataset/misc.rb', line 128

def first_source_table
  source = @opts[:from]
  if source.nil? || source.empty?
    raise Error, 'No source specified for query'
  end
  case s = source.first
  when SQL::AliasedExpression
    s.expression
  when Symbol
    sch, table, aliaz = split_symbol(s)
    aliaz ? (sch ? SQL::QualifiedIdentifier.new(sch, table) : table.to_sym) : s
  else
    s
  end
end

#for_update ⇒ Object

Returns a cloned dataset with a :update lock style.

DB[:table].for_update # SELECT * FROM table FOR UPDATE



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# File 'lib/sequel/dataset/query.rb', line 233

def for_update
   return self if opts[:lock] == :update
  cached_dataset(:_for_update_ds){lock_style(:update)}
end

#freeze ⇒ Object

:nocov:



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# File 'lib/sequel/dataset/misc.rb', line 74

def freeze
  @opts.freeze
  super
end

#from(*source, &block) ⇒ Object

Returns a copy of the dataset with the source changed. If no source is given, removes all tables. If multiple sources are given, it is the same as using a CROSS JOIN (cartesian product) between all tables. If a block is given, it is treated as a virtual row block, similar to where.

DB[:items].from # SQL: SELECT *
DB[:items].from(:blah) # SQL: SELECT * FROM blah
DB[:items].from(:blah, :foo) # SQL: SELECT * FROM blah, foo
DB[:items].from{fun(arg)} # SQL: SELECT * FROM fun(arg)



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# File 'lib/sequel/dataset/query.rb', line 247

def from(*source, &block)
  virtual_row_columns(source, block)
  table_alias_num = 0
  ctes = nil
  source.map! do |s|
    case s
    when Dataset
      if hoist_cte?(s)
        ctes ||= []
        ctes += s.opts[:with]
        s = s.clone(:with=>nil)
      end
      SQL::AliasedExpression.new(s, dataset_alias(table_alias_num+=1))
    when Symbol
      sch, table, aliaz = split_symbol(s)
      if aliaz
        s = sch ? SQL::QualifiedIdentifier.new(sch, table) : SQL::Identifier.new(table)
        SQL::AliasedExpression.new(s, aliaz.to_sym)
      else
        s
      end
    else
      s
    end
  end
  o = {:from=>source.empty? ? nil : source.freeze}
  o[:with] = ((opts[:with] || EMPTY_ARRAY) + ctes).freeze if ctes
  o[:num_dataset_sources] = table_alias_num if table_alias_num > 0
  clone(o)
end

#from_self(opts = OPTS) ⇒ Object

Returns a dataset selecting from the current dataset. Options:

:alias

Controls the alias of the table

:column_aliases

Also aliases columns, using derived column lists. Only used in conjunction with :alias.

ds = DB[:items].order(:name).select(:id, :name)
# SELECT id,name FROM items ORDER BY name

ds.from_self
# SELECT * FROM (SELECT id, name FROM items ORDER BY name) AS t1

ds.from_self(alias: :foo)
# SELECT * FROM (SELECT id, name FROM items ORDER BY name) AS foo

ds.from_self(alias: :foo, column_aliases: [:c1, :c2])
# SELECT * FROM (SELECT id, name FROM items ORDER BY name) AS foo(c1, c2)



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# File 'lib/sequel/dataset/query.rb', line 295

def from_self(opts=OPTS)
  fs = {}
  @opts.keys.each{|k| fs[k] = nil unless non_sql_option?(k)}
  pr = proc do
    c = clone(fs).from(opts[:alias] ? as(opts[:alias], opts[:column_aliases]) : self)
    if cols = _columns
      c.send(:columns=, cols)
    end
    c
  end

  opts.empty? ? cached_dataset(:_from_self_ds, &pr) : pr.call
end

#frozen? ⇒ Boolean

:nodoc:

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/misc.rb', line 84

def frozen?  # :nodoc:
  true
end

#function_sql_append(sql, f) ⇒ Object

Append literalization of function call to SQL string.



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# File 'lib/sequel/dataset/sql.rb', line 488

def function_sql_append(sql, f)
  name = f.name
  opts = f.opts

  if opts[:emulate]
    if emulate_function?(name)
      emulate_function_sql_append(sql, f)
      return
    end

    name = native_function_name(name) 
  end

  sql << 'LATERAL ' if opts[:lateral]

  case name
  when SQL::Identifier
    if supports_quoted_function_names? && opts[:quoted]
      literal_append(sql, name)
    else
      sql << name.value.to_s
    end
  when SQL::QualifiedIdentifier
    if supports_quoted_function_names? && opts[:quoted] != false
      literal_append(sql, name)
    else
      sql << split_qualifiers(name).join('.')
    end
  else
    if supports_quoted_function_names? && opts[:quoted]
      quote_identifier_append(sql, name)
    else
      sql << name.to_s
    end
  end

  sql << '('
  if filter = opts[:filter]
    filter = filter_expr(filter, &opts[:filter_block])
  end
  if opts[:*]
    if filter && !supports_filtered_aggregates?
      literal_append(sql, Sequel.case({filter=>1}, nil))
      filter = nil
    else
      sql <<  '*'
    end
  else
    sql << "DISTINCT " if opts[:distinct]
    if filter && !supports_filtered_aggregates?
      expression_list_append(sql, f.args.map{|arg| Sequel.case({filter=>arg}, nil)})
      filter = nil
    else
      expression_list_append(sql, f.args)
    end
    if order = opts[:order]
      sql << " ORDER BY "
      expression_list_append(sql, order)
    end
  end
  sql << ')'

  if group = opts[:within_group]
    sql << " WITHIN GROUP (ORDER BY "
    expression_list_append(sql, group)
    sql << ')'
  end

  if filter
    sql << " FILTER (WHERE "
    literal_append(sql, filter)
    sql << ')'
  end

  if window = opts[:over]
    sql << ' OVER '
    window_sql_append(sql, window.opts)
  end

  if opts[:with_ordinality]
    sql << " WITH ORDINALITY"
  end
end

#get(column = (no_arg=true; nil), &block) ⇒ Object

Return the column value for the first matching record in the dataset. Raises an error if both an argument and block is given.

DB[:table].get(:id) # SELECT id FROM table LIMIT 1
# => 3

ds.get{sum(id)} # SELECT sum(id) AS v FROM table LIMIT 1
# => 6

You can pass an array of arguments to return multiple arguments, but you must make sure each element in the array has an alias that Sequel can determine:

DB[:table].get([:id, :name]) # SELECT id, name FROM table LIMIT 1
# => [3, 'foo']

DB[:table].get{[sum(id).as(sum), name]} # SELECT sum(id) AS sum, name FROM table LIMIT 1
# => [6, 'foo']

If called on a dataset with raw SQL, returns the first value in the dataset without changing the selection or setting a limit:

DB["SELECT id FROM table"].get # SELECT id FROM table
# =>  3



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# File 'lib/sequel/dataset/actions.rb', line 291

def get(column=(no_arg=true; nil), &block)
  ds = naked
  if block
    raise(Error, 'Must call Dataset#get with an argument or a block, not both') unless no_arg
    ds = ds.select(&block)
    column = ds.opts[:select]
    column = nil if column.is_a?(Array) && column.length < 2
  elsif no_arg && opts[:sql]
    return ds.single_value!
  else
    case column
    when Array
      ds = ds.select(*column)
    when LiteralString, Symbol, SQL::Identifier, SQL::QualifiedIdentifier, SQL::AliasedExpression
      if loader = cached_placeholder_literalizer(:_get_loader) do |pl|
          ds.single_value_ds.select(pl.arg)
        end

        return loader.get(column)
      end

      ds = ds.select(column)
    else
      if loader = cached_placeholder_literalizer(:_get_alias_loader) do |pl|
          ds.single_value_ds.select(Sequel.as(pl.arg, :v))
        end

        return loader.get(column)
      end

      ds = ds.select(Sequel.as(column, :v))
    end
  end

  if column.is_a?(Array)
   if r = ds.single_record
     r.values_at(*hash_key_symbols(column))
   end
  else
    ds.single_value
  end
end

#graph(dataset, join_conditions = nil, options = OPTS, &block) ⇒ Object

Similar to Dataset#join_table, but uses unambiguous aliases for selected columns and keeps metadata about the aliases for use in other methods.

Arguments:

dataset

Can be a symbol (specifying a table), another dataset, or an SQL::Identifier, SQL::QualifiedIdentifier, or SQL::AliasedExpression.

join_conditions

Any condition(s) allowed by join_table.

block

A block that is passed to join_table.

Options:

:from_self_alias

The alias to use when the receiver is not a graphed dataset but it contains multiple FROM tables or a JOIN. In this case, the receiver is wrapped in a from_self before graphing, and this option determines the alias to use.

:implicit_qualifier

The qualifier of implicit conditions, see #join_table.

:join_only

Only join the tables, do not change the selected columns.

:join_type

The type of join to use (passed to join_table). Defaults to :left_outer.

:qualify

The type of qualification to do, see #join_table.

:select

An array of columns to select. When not used, selects all columns in the given dataset. When set to false, selects no columns and is like simply joining the tables, though graph keeps some metadata about the join that makes it important to use graph instead of join_table.

:table_alias

The alias to use for the table. If not specified, doesn’t alias the table. You will get an error if the alias (or table) name is used more than once.



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# File 'lib/sequel/dataset/graph.rb', line 53

def graph(dataset, join_conditions = nil, options = OPTS, &block)
  # Allow the use of a dataset or symbol as the first argument
  # Find the table name/dataset based on the argument
  table_alias = options[:table_alias]
  table = dataset
  create_dataset = true

  case dataset
  when Symbol
    # let alias be the same as the table name (sans any optional schema)
    # unless alias explicitly given in the symbol using ___ notation and symbol splitting is enabled
    table_alias ||= split_symbol(table).compact.last
  when Dataset
    if dataset.simple_select_all?
      table = dataset.opts[:from].first
      table_alias ||= table
    else
      table_alias ||= dataset_alias((@opts[:num_dataset_sources] || 0)+1)
    end
    create_dataset = false
  when SQL::Identifier
    table_alias ||= table.value
  when SQL::QualifiedIdentifier
    table_alias ||= split_qualifiers(table).last
  when SQL::AliasedExpression
    return graph(table.expression, join_conditions, {:table_alias=>table.alias}.merge!(options), &block)
  else
    raise Error, "The dataset argument should be a symbol or dataset"
  end
  table_alias = table_alias.to_sym

  if create_dataset
    dataset = db.from(table)
  end

  # Raise Sequel::Error with explanation that the table alias has been used
  raise_alias_error = lambda do
    raise(Error, "this #{options[:table_alias] ? 'alias' : 'table'} has already been been used, please specify " \
      "#{options[:table_alias] ? 'a different alias' : 'an alias via the :table_alias option'}") 
  end

  # Only allow table aliases that haven't been used
  raise_alias_error.call if @opts[:graph] && @opts[:graph][:table_aliases] && @opts[:graph][:table_aliases].include?(table_alias)
  
  table_alias_qualifier = qualifier_from_alias_symbol(table_alias, table)
  implicit_qualifier = options[:implicit_qualifier]
  joined_dataset = joined_dataset?
  ds = self
  graph = opts[:graph]

  if !graph && (select = @opts[:select]) && !select.empty?
    select_columns = nil

    unless !joined_dataset && select.length == 1 && (select[0].is_a?(SQL::ColumnAll))
      force_from_self = false
      select_columns = select.map do |sel|
        unless col = _hash_key_symbol(sel)
          force_from_self = true
          break
        end

        [sel, col]
      end

      select_columns = nil if force_from_self
    end
  end

  # Use a from_self if this is already a joined table (or from_self specifically disabled for graphs)
  if (@opts[:graph_from_self] != false && !graph && (joined_dataset || force_from_self))
    from_selfed = true
    implicit_qualifier = options[:from_self_alias] || first_source
    ds = ds.from_self(:alias=>implicit_qualifier)
  end
  
  # Join the table early in order to avoid cloning the dataset twice
  ds = ds.join_table(options[:join_type] || :left_outer, table, join_conditions, :table_alias=>table_alias_qualifier, :implicit_qualifier=>implicit_qualifier, :qualify=>options[:qualify], &block)

  return ds if options[:join_only]

  opts = ds.opts

  # Whether to include the table in the result set
  add_table = options[:select] == false ? false : true

  if graph
    graph = graph.dup
    select = opts[:select].dup
    [:column_aliases, :table_aliases, :column_alias_num].each{|k| graph[k] = graph[k].dup}
  else
    # Setup the initial graph data structure if it doesn't exist
    qualifier = ds.first_source_alias
    master = alias_symbol(qualifier)
    raise_alias_error.call if master == table_alias

    # Master hash storing all .graph related information
    graph = {}

    # Associates column aliases back to tables and columns
    column_aliases = graph[:column_aliases] = {}

    # Associates table alias (the master is never aliased)
    table_aliases = graph[:table_aliases] = {master=>self}

    # Keep track of the alias numbers used
    ca_num = graph[:column_alias_num] = Hash.new(0)

    select = if select_columns
      select_columns.map do |sel, column|
        column_aliases[column] = [master, column]
        if from_selfed
          # Initial dataset was wrapped in subselect, selected all
          # columns in the subselect, qualified by the subselect alias.
          Sequel.qualify(qualifier, Sequel.identifier(column))
        else
          # Initial dataset not wrapped in subslect, just make
          # sure columns are qualified in some way.
          qualified_expression(sel, qualifier)
        end
      end
    else
      columns.map do |column|
        column_aliases[column] = [master, column]
        SQL::QualifiedIdentifier.new(qualifier, column)
      end
    end
  end

  # Add the table alias to the list of aliases
  # Even if it isn't been used in the result set,
  # we add a key for it with a nil value so we can check if it
  # is used more than once
  table_aliases = graph[:table_aliases]
  table_aliases[table_alias] = add_table ? dataset : nil

  # Add the columns to the selection unless we are ignoring them
  if add_table
    column_aliases = graph[:column_aliases]
    ca_num = graph[:column_alias_num]
    # Which columns to add to the result set
    cols = options[:select] || dataset.columns
    # If the column hasn't been used yet, don't alias it.
    # If it has been used, try table_column.
    # If that has been used, try table_column_N 
    # using the next value of N that we know hasn't been
    # used
    cols.each do |column|
      col_alias, identifier = if column_aliases[column]
        column_alias = :"#{table_alias}_#{column}"
        if column_aliases[column_alias]
          column_alias_num = ca_num[column_alias]
          column_alias = :"#{column_alias}_#{column_alias_num}" 
          ca_num[column_alias] += 1
        end
        [column_alias, SQL::AliasedExpression.new(SQL::QualifiedIdentifier.new(table_alias_qualifier, column), column_alias)]
      else
        ident = SQL::QualifiedIdentifier.new(table_alias_qualifier, column)
        [column, ident]
      end
      column_aliases[col_alias] = [table_alias, column].freeze
      select.push(identifier)
    end
  end
  [:column_aliases, :table_aliases, :column_alias_num].each{|k| graph[k].freeze}
  ds = ds.clone(:graph=>graph.freeze)
  ds.select(*select)
end

#grep(columns, patterns, opts = OPTS) ⇒ Object

Match any of the columns to any of the patterns. The terms can be strings (which use LIKE) or regular expressions if the database supports that. Note that the total number of pattern matches will be Array(columns).length * Array(terms).length, which could cause performance issues.

Options (all are boolean):

:all_columns

All columns must be matched to any of the given patterns.

:all_patterns

All patterns must match at least one of the columns.

:case_insensitive

Use a case insensitive pattern match (the default is case sensitive if the database supports it).

If both :all_columns and :all_patterns are true, all columns must match all patterns.

Examples:

dataset.grep(:a, '%test%')
# SELECT * FROM items WHERE (a LIKE '%test%' ESCAPE '\')

dataset.grep([:a, :b], %w'%test% foo')
# SELECT * FROM items WHERE ((a LIKE '%test%' ESCAPE '\') OR (a LIKE 'foo' ESCAPE '\')
#   OR (b LIKE '%test%' ESCAPE '\') OR (b LIKE 'foo' ESCAPE '\'))

dataset.grep([:a, :b], %w'%foo% %bar%', all_patterns: true)
# SELECT * FROM a WHERE (((a LIKE '%foo%' ESCAPE '\') OR (b LIKE '%foo%' ESCAPE '\'))
#   AND ((a LIKE '%bar%' ESCAPE '\') OR (b LIKE '%bar%' ESCAPE '\')))

dataset.grep([:a, :b], %w'%foo% %bar%', all_columns: true)
# SELECT * FROM a WHERE (((a LIKE '%foo%' ESCAPE '\') OR (a LIKE '%bar%' ESCAPE '\'))
#   AND ((b LIKE '%foo%' ESCAPE '\') OR (b LIKE '%bar%' ESCAPE '\')))

dataset.grep([:a, :b], %w'%foo% %bar%', all_patterns: true, all_columns: true)
# SELECT * FROM a WHERE ((a LIKE '%foo%' ESCAPE '\') AND (b LIKE '%foo%' ESCAPE '\')
#   AND (a LIKE '%bar%' ESCAPE '\') AND (b LIKE '%bar%' ESCAPE '\'))



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# File 'lib/sequel/dataset/query.rb', line 344

def grep(columns, patterns, opts=OPTS)
  column_op = opts[:all_columns] ? :AND : :OR
  if opts[:all_patterns]
    conds = Array(patterns).map do |pat|
      SQL::BooleanExpression.new(column_op, *Array(columns).map{|c| SQL::StringExpression.like(c, pat, opts)})
    end
    where(SQL::BooleanExpression.new(:AND, *conds))
  else
    conds = Array(columns).map do |c|
      SQL::BooleanExpression.new(:OR, *Array(patterns).map{|pat| SQL::StringExpression.like(c, pat, opts)})
    end
    where(SQL::BooleanExpression.new(column_op, *conds))
  end
end

#group(*columns, &block) ⇒ Object

Returns a copy of the dataset with the results grouped by the value of the given columns. If a block is given, it is treated as a virtual row block, similar to where.

DB[:items].group(:id) # SELECT * FROM items GROUP BY id
DB[:items].group(:id, :name) # SELECT * FROM items GROUP BY id, name
DB[:items].group{[a, sum(b)]} # SELECT * FROM items GROUP BY a, sum(b)



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# File 'lib/sequel/dataset/query.rb', line 366

def group(*columns, &block)
  virtual_row_columns(columns, block)
  clone(:group => (columns.compact.empty? ? nil : columns.freeze))
end

#group_and_count(*columns, &block) ⇒ Object

Returns a dataset grouped by the given column with count by group. Column aliases may be supplied, and will be included in the select clause. If a block is given, it is treated as a virtual row block, similar to where.

Examples:

DB[:items].group_and_count(:name).all
# SELECT name, count(*) AS count FROM items GROUP BY name 
# => [{:name=>'a', :count=>1}, ...]

DB[:items].group_and_count(:first_name, :last_name).all
# SELECT first_name, last_name, count(*) AS count FROM items GROUP BY first_name, last_name
# => [{:first_name=>'a', :last_name=>'b', :count=>1}, ...]

DB[:items].group_and_count(Sequel[:first_name].as(:name)).all
# SELECT first_name AS name, count(*) AS count FROM items GROUP BY first_name
# => [{:name=>'a', :count=>1}, ...]

DB[:items].group_and_count{substr(:first_name, 1, 1).as(:initial)}.all
# SELECT substr(first_name, 1, 1) AS initial, count(*) AS count FROM items GROUP BY substr(first_name, 1, 1)
# => [{:initial=>'a', :count=>1}, ...]



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# File 'lib/sequel/dataset/query.rb', line 397

def group_and_count(*columns, &block)
  select_group(*columns, &block).select_append(COUNT_OF_ALL_AS_COUNT)
end

#group_append(*columns, &block) ⇒ Object

Returns a copy of the dataset with the given columns added to the list of existing columns to group on. If no existing columns are present this method simply sets the columns as the initial ones to group on.

DB[:items].group_append(:b) # SELECT * FROM items GROUP BY b
DB[:items].group(:a).group_append(:b) # SELECT * FROM items GROUP BY a, b



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# File 'lib/sequel/dataset/query.rb', line 407

def group_append(*columns, &block)
  columns = @opts[:group] + columns if @opts[:group]
  group(*columns, &block)
end

#group_by(*columns, &block) ⇒ Object

Alias of group



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# File 'lib/sequel/dataset/query.rb', line 372

def group_by(*columns, &block)
  group(*columns, &block)
end

#group_cube ⇒ Object

Adds the appropriate CUBE syntax to GROUP BY.

Raises:



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# File 'lib/sequel/dataset/query.rb', line 413

def group_cube
  raise Error, "GROUP BY CUBE not supported on #{db.database_type}" unless supports_group_cube?
  clone(:group_options=>:cube)
end

#group_rollup ⇒ Object

Adds the appropriate ROLLUP syntax to GROUP BY.

Raises:



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# File 'lib/sequel/dataset/query.rb', line 419

def group_rollup
  raise Error, "GROUP BY ROLLUP not supported on #{db.database_type}" unless supports_group_rollup?
  clone(:group_options=>:rollup)
end

#grouping_sets ⇒ Object

Adds the appropriate GROUPING SETS syntax to GROUP BY.

Raises:



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# File 'lib/sequel/dataset/query.rb', line 425

def grouping_sets
  raise Error, "GROUP BY GROUPING SETS not supported on #{db.database_type}" unless supports_grouping_sets?
  clone(:group_options=>:"grouping sets")
end

#hash ⇒ Object

Define a hash value such that datasets with the same class, DB, and opts, will have the same hash value.



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# File 'lib/sequel/dataset/misc.rb', line 146

def hash
  [self.class, db, opts].hash
end

#having(*cond, &block) ⇒ Object

Returns a copy of the dataset with the HAVING conditions changed. See #where for argument types.

DB[:items].group(:sum).having(sum: 10)
# SELECT * FROM items GROUP BY sum HAVING (sum = 10)



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# File 'lib/sequel/dataset/query.rb', line 434

def having(*cond, &block)
  add_filter(:having, cond, &block)
end

#import(columns, values, opts = OPTS) ⇒ Object

Inserts multiple records into the associated table. This method can be used to efficiently insert a large number of records into a table in a single query if the database supports it. Inserts are automatically wrapped in a transaction if necessary.

This method is called with a columns array and an array of value arrays:

DB[:table].import([:x, :y], [[1, 2], [3, 4]])
# INSERT INTO table (x, y) VALUES (1, 2) 
# INSERT INTO table (x, y) VALUES (3, 4)

or, if the database supports it:

# INSERT INTO table (x, y) VALUES (1, 2), (3, 4)

This method also accepts a dataset instead of an array of value arrays:

DB[:table].import([:x, :y], DB[:table2].select(:a, :b))
# INSERT INTO table (x, y) SELECT a, b FROM table2

Options:

:commit_every

Open a new transaction for every given number of records. For example, if you provide a value of 50, will commit after every 50 records. When a transaction is not required, this option controls the maximum number of values to insert with a single statement; it does not force the use of a transaction.

:return

When this is set to :primary_key, returns an array of autoincremented primary key values for the rows inserted. This does not have an effect if values is a Dataset.

:server

Set the server/shard to use for the transaction and insert queries.

:skip_transaction

Do not use a transaction even when using multiple INSERT queries.

:slice

Same as :commit_every, :commit_every takes precedence.

Raises:



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# File 'lib/sequel/dataset/actions.rb', line 370

def import(columns, values, opts=OPTS)
  return insert(columns, values) if values.is_a?(Dataset)

  return if values.empty?
  raise(Error, 'Using Sequel::Dataset#import with an empty column array is not allowed') if columns.empty?
  ds = opts[:server] ? server(opts[:server]) : self
  
  if slice_size = opts.fetch(:commit_every, opts.fetch(:slice, default_import_slice))
    offset = 0
    rows = []
    while offset < values.length
      rows << ds._import(columns, values[offset, slice_size], opts)
      offset += slice_size
    end
    rows.flatten
  else
    ds._import(columns, values, opts)
  end
end

#insert(*values, &block) ⇒ Object

Inserts values into the associated table. The returned value is generally the value of the autoincremented primary key for the inserted row, assuming that a single row is inserted and the table has an autoincrementing primary key.

insert handles a number of different argument formats:

no arguments or single empty hash

Uses DEFAULT VALUES

single hash

Most common format, treats keys as columns and values as values

single array

Treats entries as values, with no columns

two arrays

Treats first array as columns, second array as values

single Dataset

Treats as an insert based on a selection from the dataset given, with no columns

array and dataset

Treats as an insert based on a selection from the dataset given, with the columns given by the array.

Examples:

DB[:items].insert
# INSERT INTO items DEFAULT VALUES

DB[:items].insert({})
# INSERT INTO items DEFAULT VALUES

DB[:items].insert([1,2,3])
# INSERT INTO items VALUES (1, 2, 3)

DB[:items].insert([:a, :b], [1,2])
# INSERT INTO items (a, b) VALUES (1, 2)

DB[:items].insert(a: 1, b: 2)
# INSERT INTO items (a, b) VALUES (1, 2)

DB[:items].insert(DB[:old_items])
# INSERT INTO items SELECT * FROM old_items

DB[:items].insert([:a, :b], DB[:old_items])
# INSERT INTO items (a, b) SELECT * FROM old_items



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# File 'lib/sequel/dataset/actions.rb', line 426

def insert(*values, &block)
  sql = insert_sql(*values)
  if uses_returning?(:insert)
    returning_fetch_rows(sql, &block)
  else
    execute_insert(sql)
  end
end

#insert_sql(*values) ⇒ Object

Returns an INSERT SQL query string. See insert.

DB[:items].insert_sql(a: 1)
# => "INSERT INTO items (a) VALUES (1)"



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# File 'lib/sequel/dataset/sql.rb', line 22

def insert_sql(*values)
  return static_sql(@opts[:sql]) if @opts[:sql]

  check_insert_allowed!

  columns, values = _parse_insert_sql_args(values)
  if values.is_a?(Array) && values.empty? && !insert_supports_empty_values? 
    columns, values = insert_empty_columns_values
  elsif values.is_a?(Dataset) && hoist_cte?(values) && supports_cte?(:insert)
    ds, values = hoist_cte(values)
    return ds.clone(:columns=>columns, :values=>values).send(:_insert_sql)
  end
  clone(:columns=>columns, :values=>values).send(:_insert_sql)
end

#inspect ⇒ Object

Returns a string representation of the dataset including the class name and the corresponding SQL select statement.



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# File 'lib/sequel/dataset/misc.rb', line 152

def inspect
  "#<#{visible_class_name}: #{sql.inspect}>"
end

#intersect(dataset, opts = OPTS) ⇒ Object

Adds an INTERSECT clause using a second dataset object. An INTERSECT compound dataset returns all rows in both the current dataset and the given dataset. Raises an InvalidOperation if the operation is not supported. Options:

:alias

Use the given value as the from_self alias

:all

Set to true to use INTERSECT ALL instead of INTERSECT, so duplicate rows can occur

:from_self

Set to false to not wrap the returned dataset in a from_self, use with care.

DB[:items].intersect(DB[:other_items])
# SELECT * FROM (SELECT * FROM items INTERSECT SELECT * FROM other_items) AS t1

DB[:items].intersect(DB[:other_items], all: true, from_self: false)
# SELECT * FROM items INTERSECT ALL SELECT * FROM other_items

DB[:items].intersect(DB[:other_items], alias: :i)
# SELECT * FROM (SELECT * FROM items INTERSECT SELECT * FROM other_items) AS i

Raises:

  • (InvalidOperation) 


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# File 'lib/sequel/dataset/query.rb', line 455

def intersect(dataset, opts=OPTS)
  raise(InvalidOperation, "INTERSECT not supported") unless supports_intersect_except?
  raise(InvalidOperation, "INTERSECT ALL not supported") if opts[:all] && !supports_intersect_except_all?
  compound_clone(:intersect, dataset, opts)
end

#invert ⇒ Object

Inverts the current WHERE and HAVING clauses. If there is neither a WHERE or HAVING clause, adds a WHERE clause that is always false.

DB[:items].where(category: 'software').invert
# SELECT * FROM items WHERE (category != 'software')

DB[:items].where(category: 'software', id: 3).invert
# SELECT * FROM items WHERE ((category != 'software') OR (id != 3))

See documentation for exclude for how inversion is handled in regards to SQL 3-valued boolean logic.



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# File 'lib/sequel/dataset/query.rb', line 472

def invert
  cached_dataset(:_invert_ds) do
    having, where = @opts.values_at(:having, :where)
    if having.nil? && where.nil?
      where(false)
    else
      o = {}
      o[:having] = SQL::BooleanExpression.invert(having) if having
      o[:where] = SQL::BooleanExpression.invert(where) if where
      clone(o)
    end
  end
end

#join(*args, &block) ⇒ Object

Alias of inner_join



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# File 'lib/sequel/dataset/query.rb', line 487

def join(*args, &block)
  inner_join(*args, &block)
end

#join_clause_sql_append(sql, jc) ⇒ Object

Append literalization of JOIN clause without ON or USING to SQL string.



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# File 'lib/sequel/dataset/sql.rb', line 573

def join_clause_sql_append(sql, jc)
  table = jc.table
  table_alias = jc.table_alias
  table_alias = nil if table == table_alias && !jc.column_aliases
  sql << ' ' << join_type_sql(jc.join_type) << ' '
  identifier_append(sql, table)
  as_sql_append(sql, table_alias, jc.column_aliases) if table_alias
end

#join_on_clause_sql_append(sql, jc) ⇒ Object

Append literalization of JOIN ON clause to SQL string.



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# File 'lib/sequel/dataset/sql.rb', line 583

def join_on_clause_sql_append(sql, jc)
  join_clause_sql_append(sql, jc)
  sql << ' ON '
  literal_append(sql, filter_expr(jc.on))
end

#join_table(type, table, expr = nil, options = OPTS, &block) ⇒ Object

Returns a joined dataset. Not usually called directly, users should use the appropriate join method (e.g. join, left_join, natural_join, cross_join) which fills in the type argument.

Takes the following arguments:

type

The type of join to do (e.g. :inner)

table

table to join into the current dataset. Generally one of the following types:

String, Symbol

identifier used as table or view name

Dataset

a subselect is performed with an alias of tN for some value of N

SQL::Function

set returning function

SQL::AliasedExpression

already aliased expression. Uses given alias unless overridden by the :table_alias option.

expr

conditions used when joining, depends on type:

Hash, Array of pairs

Assumes key (1st arg) is column of joined table (unless already qualified), and value (2nd arg) is column of the last joined or primary table (or the :implicit_qualifier option). To specify multiple conditions on a single joined table column, you must use an array. Uses a JOIN with an ON clause.

Array

If all members of the array are symbols, considers them as columns and uses a JOIN with a USING clause. Most databases will remove duplicate columns from the result set if this is used.

nil

If a block is not given, doesn’t use ON or USING, so the JOIN should be a NATURAL or CROSS join. If a block is given, uses an ON clause based on the block, see below.

otherwise

Treats the argument as a filter expression, so strings are considered literal, symbols specify boolean columns, and Sequel expressions can be used. Uses a JOIN with an ON clause.

options

a hash of options, with the following keys supported:

:table_alias

Override the table alias used when joining. In general you shouldn’t use this option, you should provide the appropriate SQL::AliasedExpression as the table argument.

:implicit_qualifier

The name to use for qualifying implicit conditions. By default, the last joined or primary table is used.

:join_using

Force the using of JOIN USING, even if expr is not an array of symbols.

:reset_implicit_qualifier

Can set to false to ignore this join when future joins determine qualifier for implicit conditions.

:qualify

Can be set to false to not do any implicit qualification. Can be set to :deep to use the Qualifier AST Transformer, which will attempt to qualify subexpressions of the expression tree. Can be set to :symbol to only qualify symbols. Defaults to the value of default_join_table_qualification.

block

The block argument should only be given if a JOIN with an ON clause is used, in which case it yields the table alias/name for the table currently being joined, the table alias/name for the last joined (or first table), and an array of previous SQL::JoinClause. Unlike where, this block is not treated as a virtual row block.

Examples:

DB[:a].join_table(:cross, :b)
# SELECT * FROM a CROSS JOIN b

DB[:a].join_table(:inner, DB[:b], c: d)
# SELECT * FROM a INNER JOIN (SELECT * FROM b) AS t1 ON (t1.c = a.d)

DB[:a].join_table(:left, Sequel[:b].as(:c), [:d])
# SELECT * FROM a LEFT JOIN b AS c USING (d)

DB[:a].natural_join(:b).join_table(:inner, :c) do |ta, jta, js|
  (Sequel.qualify(ta, :d) > Sequel.qualify(jta, :e)) & {Sequel.qualify(ta, :f)=>DB.from(js.first.table).select(:g)}
end
# SELECT * FROM a NATURAL JOIN b INNER JOIN c
#   ON ((c.d > b.e) AND (c.f IN (SELECT g FROM b)))



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# File 'lib/sequel/dataset/query.rb', line 551

def join_table(type, table, expr=nil, options=OPTS, &block)
  if hoist_cte?(table)
    s, ds = hoist_cte(table)
    return s.join_table(type, ds, expr, options, &block)
  end

  using_join = options[:join_using] || (expr.is_a?(Array) && !expr.empty? && expr.all?{|x| x.is_a?(Symbol)})
  if using_join && !supports_join_using?
    h = {}
    expr.each{|e| h[e] = e}
    return join_table(type, table, h, options)
  end

  table_alias = options[:table_alias]

  if table.is_a?(SQL::AliasedExpression)
    table_expr = if table_alias
      SQL::AliasedExpression.new(table.expression, table_alias, table.columns)
    else
      table
    end
    table = table_expr.expression
    table_name = table_alias = table_expr.alias
  elsif table.is_a?(Dataset)
    if table_alias.nil?
      table_alias_num = (@opts[:num_dataset_sources] || 0) + 1
      table_alias = dataset_alias(table_alias_num)
    end
    table_name = table_alias
    table_expr = SQL::AliasedExpression.new(table, table_alias)
  else
    table, implicit_table_alias = split_alias(table)
    table_alias ||= implicit_table_alias
    table_name = table_alias || table
    table_expr = table_alias ? SQL::AliasedExpression.new(table, table_alias) : table
  end

  join = if expr.nil? and !block
    SQL::JoinClause.new(type, table_expr)
  elsif using_join
    raise(Sequel::Error, "can't use a block if providing an array of symbols as expr") if block
    SQL::JoinUsingClause.new(expr, type, table_expr)
  else
    last_alias = options[:implicit_qualifier] || @opts[:last_joined_table] || first_source_alias
    qualify_type = options[:qualify]
    if Sequel.condition_specifier?(expr)
      expr = expr.map do |k, v|
        qualify_type = default_join_table_qualification if qualify_type.nil?
        case qualify_type
        when false
          nil # Do no qualification
        when :deep
          k = Sequel::Qualifier.new(table_name).transform(k)
          v = Sequel::Qualifier.new(last_alias).transform(v)
        else
          k = qualified_column_name(k, table_name) if k.is_a?(Symbol)
          v = qualified_column_name(v, last_alias) if v.is_a?(Symbol)
        end
        [k,v]
      end
      expr = SQL::BooleanExpression.from_value_pairs(expr)
    end
    if block
      expr2 = yield(table_name, last_alias, @opts[:join] || EMPTY_ARRAY)
      expr = expr ? SQL::BooleanExpression.new(:AND, expr, expr2) : expr2
    end
    SQL::JoinOnClause.new(expr, type, table_expr)
  end

  opts = {:join => ((@opts[:join] || EMPTY_ARRAY) + [join]).freeze}
  opts[:last_joined_table] = table_name unless options[:reset_implicit_qualifier] == false
  opts[:num_dataset_sources] = table_alias_num if table_alias_num
  clone(opts)
end

#join_using_clause_sql_append(sql, jc) ⇒ Object

Append literalization of JOIN USING clause to SQL string.



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# File 'lib/sequel/dataset/sql.rb', line 590

def join_using_clause_sql_append(sql, jc)
  join_clause_sql_append(sql, jc)
  join_using_clause_using_sql_append(sql, jc.using) 
end

#joined_dataset? ⇒ Boolean

Whether this dataset is a joined dataset (multiple FROM tables or any JOINs).

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/misc.rb', line 157

def joined_dataset?
 !!((opts[:from].is_a?(Array) && opts[:from].size > 1) || opts[:join])
end

#last(*args, &block) ⇒ Object

Reverses the order and then runs #first with the given arguments and block. Note that this will not necessarily give you the last record in the dataset, unless you have an unambiguous order. If there is not currently an order for this dataset, raises an Error.

DB[:table].order(:id).last # SELECT * FROM table ORDER BY id DESC LIMIT 1
# => {:id=>10}

DB[:table].order(Sequel.desc(:id)).last(2) # SELECT * FROM table ORDER BY id ASC LIMIT 2
# => [{:id=>1}, {:id=>2}]

Raises:



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# File 'lib/sequel/dataset/actions.rb', line 445

def last(*args, &block)
  raise(Error, 'No order specified') unless @opts[:order]
  reverse.first(*args, &block)
end

#lateral ⇒ Object

Marks this dataset as a lateral dataset. If used in another dataset’s FROM or JOIN clauses, it will surround the subquery with LATERAL to enable it to deal with previous tables in the query:

DB.from(:a, DB[:b].where(Sequel[:a][:c]=>Sequel[:b][:d]).lateral)
# SELECT * FROM a, LATERAL (SELECT * FROM b WHERE (a.c = b.d))



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# File 'lib/sequel/dataset/query.rb', line 645

def lateral
  return self if opts[:lateral]
  cached_dataset(:_lateral_ds){clone(:lateral=>true)}
end

#limit(l, o = (no_offset = true; nil)) ⇒ Object

If given an integer, the dataset will contain only the first l results. If given a range, it will contain only those at offsets within that range. If a second argument is given, it is used as an offset. To use an offset without a limit, pass nil as the first argument.

DB[:items].limit(10) # SELECT * FROM items LIMIT 10
DB[:items].limit(10, 20) # SELECT * FROM items LIMIT 10 OFFSET 20
DB[:items].limit(10...20) # SELECT * FROM items LIMIT 10 OFFSET 10
DB[:items].limit(10..20) # SELECT * FROM items LIMIT 11 OFFSET 10
DB[:items].limit(nil, 20) # SELECT * FROM items OFFSET 20



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# File 'lib/sequel/dataset/query.rb', line 660

def limit(l, o = (no_offset = true; nil))
  return from_self.limit(l, o) if @opts[:sql]

  if l.is_a?(Range)
    no_offset = false
    o = l.first
    l = l.last - l.first + (l.exclude_end? ? 0 : 1)
  end
  l = l.to_i if l.is_a?(String) && !l.is_a?(LiteralString)
  if l.is_a?(Integer)
    raise(Error, 'Limits must be greater than or equal to 1') unless l >= 1
  end

  ds = clone(:limit=>l)
  ds = ds.offset(o) unless no_offset
  ds
end

#literal_append(sql, v) ⇒ Object

Append a literal representation of a value to the given SQL string.

If an unsupported object is given, an Error is raised.



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# File 'lib/sequel/dataset/sql.rb', line 40

def literal_append(sql, v)
  case v
  when Symbol
    if skip_symbol_cache?
      literal_symbol_append(sql, v)
    else 
      unless l = db.literal_symbol(v)
        l = String.new
        literal_symbol_append(l, v)
        db.literal_symbol_set(v, l)
      end
      sql << l
    end
  when String
    case v
    when LiteralString
      sql << v
    when SQL::Blob
      literal_blob_append(sql, v)
    else
      literal_string_append(sql, v)
    end
  when Integer
    sql << literal_integer(v)
  when Hash
    literal_hash_append(sql, v)
  when SQL::Expression
    literal_expression_append(sql, v)
  when Float
    sql << literal_float(v)
  when BigDecimal
    sql << literal_big_decimal(v)
  when NilClass
    sql << literal_nil
  when TrueClass
    sql << literal_true
  when FalseClass
    sql << literal_false
  when Array
    literal_array_append(sql, v)
  when Time
    v.is_a?(SQLTime) ? literal_sqltime_append(sql, v) : literal_time_append(sql, v)
  when DateTime
    literal_datetime_append(sql, v)
  when Date
    literal_date_append(sql, v)
  when Dataset
    literal_dataset_append(sql, v)
  else
    literal_other_append(sql, v)
  end
end

#literal_date_or_time(dt, raw = false) ⇒ Object

Literalize a date or time value, as a SQL string value with no typecasting. If raw is true, remove the surrounding single quotes. This is designed for usage by bound argument code that can work even if the auto_cast_date_and_time extension is used (either manually or implicitly in the related adapter).



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# File 'lib/sequel/dataset/sql.rb', line 123

def literal_date_or_time(dt, raw=false)
  value = case dt
  when SQLTime
    literal_sqltime(dt)
  when Time
    literal_time(dt)
  when DateTime
    literal_datetime(dt)
  when Date
    literal_date(dt)
  else
    raise TypeError, "unsupported type: #{dt.inspect}"
  end

  if raw
    value.sub!(/\A'/, '')
    value.sub!(/'\z/, '')
  end

  value
end

#lock_style(style) ⇒ Object

Returns a cloned dataset with the given lock style. If style is a string, it will be used directly. You should never pass a string to this method that is derived from user input, as that can lead to SQL injection.

A symbol may be used for database independent locking behavior, but all supported symbols have separate methods (e.g. for_update).

DB[:items].lock_style('FOR SHARE NOWAIT')
# SELECT * FROM items FOR SHARE NOWAIT
DB[:items].lock_style('FOR UPDATE OF table1 SKIP LOCKED')
# SELECT * FROM items FOR UPDATE OF table1 SKIP LOCKED



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# File 'lib/sequel/dataset/query.rb', line 690

def lock_style(style)
  clone(:lock => style)
end

#map(column = nil, &block) ⇒ Object

Maps column values for each record in the dataset (if an argument is given) or performs the stock mapping functionality of Enumerable otherwise. Raises an Error if both an argument and block are given.

DB[:table].map(:id) # SELECT * FROM table
# => [1, 2, 3, ...]

DB[:table].map{|r| r[:id] * 2} # SELECT * FROM table
# => [2, 4, 6, ...]

You can also provide an array of column names:

DB[:table].map([:id, :name]) # SELECT * FROM table
# => [[1, 'A'], [2, 'B'], [3, 'C'], ...]



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# File 'lib/sequel/dataset/actions.rb', line 464

def map(column=nil, &block)
  if column
    raise(Error, 'Must call Dataset#map with either an argument or a block, not both') if block
    return naked.map(column) if row_proc
    if column.is_a?(Array)
      super(){|r| r.values_at(*column)}
    else
      super(){|r| r[column]}
    end
  else
    super(&block)
  end
end

#max(arg = (no_arg = true), &block) ⇒ Object

Returns the maximum value for the given column/expression. Uses a virtual row block if no argument is given.

DB[:table].max(:id) # SELECT max(id) FROM table LIMIT 1
# => 10
DB[:table].max{function(column)} # SELECT max(function(column)) FROM table LIMIT 1
# => 7



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# File 'lib/sequel/dataset/actions.rb', line 485

def max(arg=(no_arg = true), &block)
  arg = Sequel.virtual_row(&block) if no_arg
  _aggregate(:max, arg)
end

#merge ⇒ Object

Execute a MERGE statement, which allows for INSERT, UPDATE, and DELETE behavior in a single query, based on whether rows from a source table match rows in the current table, based on the join conditions.

Unless the dataset uses static SQL, to use #merge, you must first have called #merge_using to specify the merge source and join conditions. You will then likely to call one or more of the following methods to specify MERGE behavior by adding WHEN [NOT] MATCHED clauses:

  • #merge_insert

  • #merge_update

  • #merge_delete

The WHEN [NOT] MATCHED clauses are added to the SQL in the order these methods were called on the dataset. If none of these methods are called, an error is raised.

Example:

DB[:m1]
  merge_using(:m2, i1: :i2).
  merge_insert(i1: :i2, a: Sequel[:b]+11).
  merge_delete{a > 30}.
  merge_update(i1: Sequel[:i1]+:i2+10, a: Sequel[:a]+:b+20).
  merge

SQL:

MERGE INTO m1 USING m2 ON (i1 = i2)
WHEN NOT MATCHED THEN INSERT (i1, a) VALUES (i2, (b + 11))
WHEN MATCHED AND (a > 30) THEN DELETE
WHEN MATCHED THEN UPDATE SET i1 = (i1 + i2 + 10), a = (a + b + 20)

On PostgreSQL, two additional merge methods are supported, for the PostgreSQL-specific DO NOTHING syntax.

  • #merge_do_nothing_when_matched

  • #merge_do_nothing_when_not_matched

This method is supported on Oracle, but Oracle’s MERGE support is non-standard, and has the following issues:

  • DELETE clause requires UPDATE clause

  • DELETE clause requires a condition

  • DELETE clause only affects rows updated by UPDATE clause



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# File 'lib/sequel/dataset/actions.rb', line 535

def merge
  execute_ddl(merge_sql)
end

#merge_delete(&block) ⇒ Object

Return a dataset with a WHEN MATCHED THEN DELETE clause added to the MERGE statement. If a block is passed, treat it as a virtual row and use it as additional conditions for the match.

merge_delete
# WHEN MATCHED THEN DELETE

merge_delete{a > 30}
# WHEN MATCHED AND (a > 30) THEN DELETE



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# File 'lib/sequel/dataset/query.rb', line 703

def merge_delete(&block)
  _merge_when(:type=>:delete, &block)
end

#merge_insert(*values, &block) ⇒ Object

Return a dataset with a WHEN NOT MATCHED THEN INSERT clause added to the MERGE statement. If a block is passed, treat it as a virtual row and use it as additional conditions for the match.

The arguments provided can be any arguments that would be accepted by #insert.

merge_insert(i1: :i2, a: Sequel[:b]+11)
# WHEN NOT MATCHED THEN INSERT (i1, a) VALUES (i2, (b + 11))

merge_insert(:i2, Sequel[:b]+11){a > 30}
# WHEN NOT MATCHED AND (a > 30) THEN INSERT VALUES (i2, (b + 11))



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# File 'lib/sequel/dataset/query.rb', line 719

def merge_insert(*values, &block)
  _merge_when(:type=>:insert, :values=>values, &block)
end

#merge_sql ⇒ Object

The SQL to use for the MERGE statement.

Raises:



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# File 'lib/sequel/dataset/sql.rb', line 94

def merge_sql
  raise Error, "This database doesn't support MERGE" unless supports_merge?
  if sql = opts[:sql]
    return static_sql(sql)
  end
  if sql = cache_get(:_merge_sql)
    return sql
  end
  source, join_condition = @opts[:merge_using]
  raise Error, "No USING clause for MERGE" unless source
  sql = @opts[:append_sql] || sql_string_origin

  select_with_sql(sql)
  sql << "MERGE INTO "
  source_list_append(sql, @opts[:from])
  sql << " USING "
  identifier_append(sql, source)
  sql << " ON "
  literal_append(sql, join_condition)
  _merge_when_sql(sql)
  cache_set(:_merge_sql, sql) if cache_sql?
  sql
end

#merge_update(values, &block) ⇒ Object

Return a dataset with a WHEN MATCHED THEN UPDATE clause added to the MERGE statement. If a block is passed, treat it as a virtual row and use it as additional conditions for the match.

merge_update(i1: Sequel[:i1]+:i2+10, a: Sequel[:a]+:b+20)
# WHEN MATCHED THEN UPDATE SET i1 = (i1 + i2 + 10), a = (a + b + 20)

merge_update(i1: :i2){a > 30}
# WHEN MATCHED AND (a > 30) THEN UPDATE SET i1 = i2



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# File 'lib/sequel/dataset/query.rb', line 732

def merge_update(values, &block)
  _merge_when(:type=>:update, :values=>values, &block)
end

#merge_using(source, join_condition) ⇒ Object

Return a dataset with the source and join condition to use for the MERGE statement.

merge_using(:m2, i1: :i2)
# USING m2 ON (i1 = i2)



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# File 'lib/sequel/dataset/query.rb', line 740

def merge_using(source, join_condition)
  clone(:merge_using => [source, join_condition].freeze)
end

#min(arg = (no_arg = true), &block) ⇒ Object

Returns the minimum value for the given column/expression. Uses a virtual row block if no argument is given.

DB[:table].min(:id) # SELECT min(id) FROM table LIMIT 1
# => 1
DB[:table].min{function(column)} # SELECT min(function(column)) FROM table LIMIT 1
# => 0



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# File 'lib/sequel/dataset/actions.rb', line 546

def min(arg=(no_arg = true), &block)
  arg = Sequel.virtual_row(&block) if no_arg
  _aggregate(:min, arg)
end

#multi_insert(hashes, opts = OPTS) ⇒ Object

This is a front end for import that allows you to submit an array of hashes instead of arrays of columns and values:

DB[:table].multi_insert([{x: 1}, {x: 2}])
# INSERT INTO table (x) VALUES (1)
# INSERT INTO table (x) VALUES (2)

Be aware that all hashes should have the same keys if you use this calling method, otherwise some columns could be missed or set to null instead of to default values.

This respects the same options as #import.



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# File 'lib/sequel/dataset/actions.rb', line 563

def multi_insert(hashes, opts=OPTS)
  return if hashes.empty?
  columns = hashes.first.keys
  import(columns, hashes.map{|h| columns.map{|c| h[c]}}, opts)
end

#multi_insert_sql(columns, values) ⇒ Object

Returns an array of insert statements for inserting multiple records. This method is used by multi_insert to format insert statements and expects a keys array and and an array of value arrays.



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# File 'lib/sequel/dataset/sql.rb', line 148

def multi_insert_sql(columns, values)
  case multi_insert_sql_strategy
  when :values
    sql = LiteralString.new('VALUES ')
    expression_list_append(sql, values.map{|r| Array(r)})
    [insert_sql(columns, sql)]
  when :union
    c = false
    sql = LiteralString.new
    u = ' UNION ALL SELECT '
    f = empty_from_sql
    values.each do |v|
      if c
        sql << u
      else
        sql << 'SELECT '
        c = true
      end
      expression_list_append(sql, v)
      sql << f if f
    end
    [insert_sql(columns, sql)]
  else
    values.map{|r| insert_sql(columns, r)}
  end
end

#naked ⇒ Object

Returns a cloned dataset without a row_proc.

ds = DB[:items].with_row_proc(:invert.to_proc)
ds.all # => [{2=>:id}]
ds.naked.all # => [{:id=>2}]



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# File 'lib/sequel/dataset/query.rb', line 749

def naked
  return self unless opts[:row_proc]
  cached_dataset(:_naked_ds){with_row_proc(nil)}
end

#negative_boolean_constant_sql_append(sql, constant) ⇒ Object

Append literalization of negative boolean constant to SQL string.



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# File 'lib/sequel/dataset/sql.rb', line 596

def negative_boolean_constant_sql_append(sql, constant)
  sql << 'NOT '
  boolean_constant_sql_append(sql, constant)
end

#nowait ⇒ Object

Returns a copy of the dataset that will raise a DatabaseLockTimeout instead of waiting for rows that are locked by another transaction

DB[:items].for_update.nowait
# SELECT * FROM items FOR UPDATE NOWAIT



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# File 'lib/sequel/dataset/query.rb', line 759

def nowait
  return self if opts[:nowait]
  cached_dataset(:_nowait_ds) do
    raise(Error, 'This dataset does not support raises errors instead of waiting for locked rows') unless supports_nowait?
    clone(:nowait=>true)
  end
end

#offset(o) ⇒ Object

Returns a copy of the dataset with a specified order. Can be safely combined with limit. If you call limit with an offset, it will override the offset if you’ve called offset first.

DB[:items].offset(10) # SELECT * FROM items OFFSET 10



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# File 'lib/sequel/dataset/query.rb', line 772

def offset(o)
  o = o.to_i if o.is_a?(String) && !o.is_a?(LiteralString)
  if o.is_a?(Integer)
    raise(Error, 'Offsets must be greater than or equal to 0') unless o >= 0
  end
  clone(:offset => o)
end

#or(*cond, &block) ⇒ Object

Adds an alternate filter to an existing WHERE clause using OR. If there is no WHERE clause, then the default is WHERE true, and OR would be redundant, so return the dataset in that case.

DB[:items].where(:a).or(:b) # SELECT * FROM items WHERE a OR b
DB[:items].or(:b) # SELECT * FROM items



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# File 'lib/sequel/dataset/query.rb', line 786

def or(*cond, &block)
  if @opts[:where].nil?
    self
  else
    add_filter(:where, cond, false, :OR, &block)
  end
end

#order(*columns, &block) ⇒ Object

Returns a copy of the dataset with the order changed. If the dataset has an existing order, it is ignored and overwritten with this order. If a nil is given the returned dataset has no order. This can accept multiple arguments of varying kinds, such as SQL functions. If a block is given, it is treated as a virtual row block, similar to where.

DB[:items].order(:name) # SELECT * FROM items ORDER BY name
DB[:items].order(:a, :b) # SELECT * FROM items ORDER BY a, b
DB[:items].order(Sequel.lit('a + b')) # SELECT * FROM items ORDER BY a + b
DB[:items].order(Sequel[:a] + :b) # SELECT * FROM items ORDER BY (a + b)
DB[:items].order(Sequel.desc(:name)) # SELECT * FROM items ORDER BY name DESC
DB[:items].order(Sequel.asc(:name, nulls: :last)) # SELECT * FROM items ORDER BY name ASC NULLS LAST
DB[:items].order{sum(name).desc} # SELECT * FROM items ORDER BY sum(name) DESC
DB[:items].order(nil) # SELECT * FROM items



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# File 'lib/sequel/dataset/query.rb', line 808

def order(*columns, &block)
  virtual_row_columns(columns, block)
  clone(:order => (columns.compact.empty?) ? nil : columns.freeze)
end

#order_append(*columns, &block) ⇒ Object

Returns a copy of the dataset with the order columns added to the end of the existing order.

DB[:items].order(:a).order(:b) # SELECT * FROM items ORDER BY b
DB[:items].order(:a).order_append(:b) # SELECT * FROM items ORDER BY a, b



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# File 'lib/sequel/dataset/query.rb', line 818

def order_append(*columns, &block)
  columns = @opts[:order] + columns if @opts[:order]
  order(*columns, &block)
end

#order_by(*columns, &block) ⇒ Object

Alias of order



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# File 'lib/sequel/dataset/query.rb', line 824

def order_by(*columns, &block)
  order(*columns, &block)
end

#order_more(*columns, &block) ⇒ Object

Alias of order_append.



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# File 'lib/sequel/dataset/query.rb', line 829

def order_more(*columns, &block)
  order_append(*columns, &block)
end

#order_prepend(*columns, &block) ⇒ Object

Returns a copy of the dataset with the order columns added to the beginning of the existing order.

DB[:items].order(:a).order(:b) # SELECT * FROM items ORDER BY b
DB[:items].order(:a).order_prepend(:b) # SELECT * FROM items ORDER BY b, a



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# File 'lib/sequel/dataset/query.rb', line 838

def order_prepend(*columns, &block)
  ds = order(*columns, &block)
  @opts[:order] ? ds.order_append(*@opts[:order]) : ds
end

#ordered_expression_sql_append(sql, oe) ⇒ Object

Append literalization of ordered expression to SQL string.



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# File 'lib/sequel/dataset/sql.rb', line 602

def ordered_expression_sql_append(sql, oe)
  if emulate = requires_emulating_nulls_first?
    case oe.nulls
    when :first
      null_order = 0
    when :last
      null_order = 2
    end

    if null_order
      literal_append(sql, Sequel.case({{oe.expression=>nil}=>null_order}, 1))
      sql << ", "
    end
  end

  literal_append(sql, oe.expression)
  sql << (oe.descending ? ' DESC' : ' ASC')

  unless emulate
    case oe.nulls
    when :first
      sql << " NULLS FIRST"
    when :last
      sql << " NULLS LAST"
    end
  end
end

#paged_each(opts = OPTS) ⇒ Object

Yields each row in the dataset, but internally uses multiple queries as needed to process the entire result set without keeping all rows in the dataset in memory, even if the underlying driver buffers all query results in memory.

Because this uses multiple queries internally, in order to remain consistent, it also uses a transaction internally. Additionally, to work correctly, the dataset must have unambiguous order. Using an ambiguous order can result in an infinite loop, as well as subtler bugs such as yielding duplicate rows or rows being skipped.

Sequel checks that the datasets using this method have an order, but it cannot ensure that the order is unambiguous.

Note that this method is not safe to use on many adapters if you are running additional queries inside the provided block. If you are running queries inside the block, use a separate thread or shard inside paged_each.

Options:

:rows_per_fetch

The number of rows to fetch per query. Defaults to 1000.

:strategy

The strategy to use for paging of results. By default this is :offset, for using an approach with a limit and offset for every page. This can be set to :filter, which uses a limit and a filter that excludes rows from previous pages. In order for this strategy to work, you must be selecting the columns you are ordering by, and none of the columns can contain NULLs. Note that some Sequel adapters have optimized implementations that will use cursors or streaming regardless of the :strategy option used.

:filter_values

If the strategy: :filter option is used, this option should be a proc that accepts the last retrieved row for the previous page and an array of ORDER BY expressions, and returns an array of values relating to those expressions for the last retrieved row. You will need to use this option if your ORDER BY expressions are not simple columns, if they contain qualified identifiers that would be ambiguous unqualified, if they contain any identifiers that are aliased in SELECT, and potentially other cases.

:skip_transaction

Do not use a transaction. This can be useful if you want to prevent a lock on the database table, at the expense of consistency.

Examples:

DB[:table].order(:id).paged_each{|row| }
# SELECT * FROM table ORDER BY id LIMIT 1000
# SELECT * FROM table ORDER BY id LIMIT 1000 OFFSET 1000
# ...

DB[:table].order(:id).paged_each(rows_per_fetch: 100){|row| }
# SELECT * FROM table ORDER BY id LIMIT 100
# SELECT * FROM table ORDER BY id LIMIT 100 OFFSET 100
# ...

DB[:table].order(:id).paged_each(strategy: :filter){|row| }
# SELECT * FROM table ORDER BY id LIMIT 1000
# SELECT * FROM table WHERE id > 1001 ORDER BY id LIMIT 1000
# ...

DB[:table].order(:id).paged_each(strategy: :filter,
  filter_values: lambda{|row, exprs| [row[:id]]}){|row| }
# SELECT * FROM table ORDER BY id LIMIT 1000
# SELECT * FROM table WHERE id > 1001 ORDER BY id LIMIT 1000
# ...



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# File 'lib/sequel/dataset/actions.rb', line 626

def paged_each(opts=OPTS)
  unless @opts[:order]
    raise Sequel::Error, "Dataset#paged_each requires the dataset be ordered"
  end
  unless defined?(yield)
    return enum_for(:paged_each, opts)
  end

  total_limit = @opts[:limit]
  offset = @opts[:offset]
  if server = @opts[:server]
    opts = Hash[opts]
    opts[:server] = server
  end

  rows_per_fetch = opts[:rows_per_fetch] || 1000
  strategy = if offset || total_limit
    :offset
  else
    opts[:strategy] || :offset
  end

  db.transaction(opts) do
    case strategy
    when :filter
      filter_values = opts[:filter_values] || proc{|row, exprs| exprs.map{|e| row[hash_key_symbol(e)]}}
      base_ds = ds = limit(rows_per_fetch)
      while ds
        last_row = nil
        ds.each do |row|
          last_row = row
          yield row
        end
        ds = (base_ds.where(ignore_values_preceding(last_row, &filter_values)) if last_row)
      end
    else
      offset ||= 0
      num_rows_yielded = rows_per_fetch
      total_rows = 0

      while num_rows_yielded == rows_per_fetch && (total_limit.nil? || total_rows < total_limit)
        if total_limit && total_rows + rows_per_fetch > total_limit
          rows_per_fetch = total_limit - total_rows
        end

        num_rows_yielded = 0
        limit(rows_per_fetch, offset).each do |row|
          num_rows_yielded += 1
          total_rows += 1 if total_limit
          yield row
        end

        offset += rows_per_fetch
      end
    end
  end

  self
end

#placeholder_literal_string_sql_append(sql, pls) ⇒ Object

Append literalization of placeholder literal string to SQL string.



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# File 'lib/sequel/dataset/sql.rb', line 631

def placeholder_literal_string_sql_append(sql, pls)
  args = pls.args
  str = pls.str
  sql << '(' if pls.parens
  if args.is_a?(Hash)
    if args.empty?
      sql << str
    else
      re = /:(#{args.keys.map{|k| Regexp.escape(k.to_s)}.join('|')})\b/
      while true
        previous, q, str = str.partition(re)
        sql << previous
        literal_append(sql, args[($1||q[1..-1].to_s).to_sym]) unless q.empty?
        break if str.empty?
      end
    end
  elsif str.is_a?(Array)
    len = args.length
    str.each_with_index do |s, i|
      sql << s
      literal_append(sql, args[i]) unless i == len
    end
    unless str.length == args.length || str.length == args.length + 1
      raise Error, "Mismatched number of placeholders (#{str.length}) and placeholder arguments (#{args.length}) when using placeholder array"
    end
  else
    i = -1
    match_len = args.length - 1
    while true
      previous, q, str = str.partition('?')
      sql << previous
      literal_append(sql, args.at(i+=1)) unless q.empty?
      if str.empty?
        unless i == match_len
          raise Error, "Mismatched number of placeholders (#{i+1}) and placeholder arguments (#{args.length}) when using placeholder string"
        end
        break
      end
    end
  end
  sql << ')' if pls.parens
end

#placeholder_literalizer_class ⇒ Object

The class to use for placeholder literalizers for the current dataset.



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# File 'lib/sequel/dataset/misc.rb', line 162

def placeholder_literalizer_class
  ::Sequel::Dataset::PlaceholderLiteralizer
end

#placeholder_literalizer_loader(&block) ⇒ Object

A placeholder literalizer loader for the current dataset.



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# File 'lib/sequel/dataset/misc.rb', line 167

def placeholder_literalizer_loader(&block)
  placeholder_literalizer_class.loader(self, &block)
end

#prepare(type, name, *values) ⇒ Object

Prepare an SQL statement for later execution. Takes a type similar to #call, and the name symbol of the prepared statement.

This returns a clone of the dataset extended with PreparedStatementMethods, which you can call with the hash of bind variables to use. The prepared statement is also stored in the associated Database, where it can be called by name. The following usage is identical:

ps = DB[:table].where(name: :$name).prepare(:first, :select_by_name)

ps.call(name: 'Blah')
# SELECT * FROM table WHERE name = ? -- ('Blah')
# => {:id=>1, :name=>'Blah'}

DB.call(:select_by_name, name: 'Blah') # Same thing



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# File 'lib/sequel/dataset/prepared_statements.rb', line 373

def prepare(type, name, *values)
  ps = to_prepared_statement(type, values, :name=>name, :extend=>prepared_statement_modules, :no_delayed_evaluations=>true)

  ps = if ps.send(:emulate_prepared_statements?)
    ps = ps.with_extend(EmulatePreparedStatementMethods)
    ps.send(:emulated_prepared_statement, type, name, values)
  else
    sql = ps.prepared_sql
    ps.prepared_args.freeze
    ps.clone(:prepared_sql=>sql, :sql=>sql)
  end

  db.set_prepared_statement(name, ps)
  ps
end

#provides_accurate_rows_matched? ⇒ Boolean

Whether this dataset will provide accurate number of rows matched for delete and update statements, true by default. Accurate in this case is the number of rows matched by the dataset’s filter.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 19

def provides_accurate_rows_matched?
  true
end

#qualified_identifier_sql_append(sql, table, column = (c = table.column; table = table.table; c)) ⇒ Object

Append literalization of qualified identifier to SQL string. If 3 arguments are given, the 2nd should be the table/qualifier and the third should be column/qualified. If 2 arguments are given, the 2nd should be an SQL::QualifiedIdentifier.



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# File 'lib/sequel/dataset/sql.rb', line 677

def qualified_identifier_sql_append(sql, table, column=(c = table.column; table = table.table; c))
  identifier_append(sql, table)
  sql << '.'
  identifier_append(sql, column)
end

#qualify(table = (cache=true; first_source)) ⇒ Object

Qualify to the given table, or first source if no table is given.

DB[:items].where(id: 1).qualify
# SELECT items.* FROM items WHERE (items.id = 1)

DB[:items].where(id: 1).qualify(:i)
# SELECT i.* FROM items WHERE (i.id = 1)



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# File 'lib/sequel/dataset/query.rb', line 850

def qualify(table=(cache=true; first_source))
  o = @opts
  return self if o[:sql]

  pr = proc do
    h = {}
    (o.keys & QUALIFY_KEYS).each do |k|
      h[k] = qualified_expression(o[k], table)
    end
    h[:select] = [SQL::ColumnAll.new(table)].freeze if !o[:select] || o[:select].empty?
    clone(h)
  end

  cache ? cached_dataset(:_qualify_ds, &pr) : pr.call
end

#quote_identifier_append(sql, name) ⇒ Object

Append literalization of unqualified identifier to SQL string. Adds quoting to identifiers (columns and tables). If identifiers are not being quoted, returns name as a string. If identifiers are being quoted quote the name with quoted_identifier.



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# File 'lib/sequel/dataset/sql.rb', line 687

def quote_identifier_append(sql, name)
  if name.is_a?(LiteralString)
    sql << name
  else
    name = name.value if name.is_a?(SQL::Identifier)
    name = input_identifier(name)
    if quote_identifiers?
      quoted_identifier_append(sql, name)
    else
      sql << name
    end
  end
end

#quote_identifiers? ⇒ Boolean

Whether this dataset quotes identifiers.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 12

def quote_identifiers?
  @opts.fetch(:quote_identifiers, true)
end

#quote_schema_table_append(sql, table) ⇒ Object

Append literalization of identifier or unqualified identifier to SQL string.



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# File 'lib/sequel/dataset/sql.rb', line 702

def quote_schema_table_append(sql, table)
  schema, table = schema_and_table(table)
  if schema
    quote_identifier_append(sql, schema)
    sql << '.'
  end
  quote_identifier_append(sql, table)
end

#quoted_identifier_append(sql, name) ⇒ Object

Append literalization of quoted identifier to SQL string. This method quotes the given name with the SQL standard double quote. should be overridden by subclasses to provide quoting not matching the SQL standard, such as backtick (used by MySQL and SQLite).



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# File 'lib/sequel/dataset/sql.rb', line 715

def quoted_identifier_append(sql, name)
  sql << '"' << name.to_s.gsub('"', '""') << '"'
end

#recursive_cte_requires_column_aliases? ⇒ Boolean

Whether you must use a column alias list for recursive CTEs, false by default.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 24

def recursive_cte_requires_column_aliases?
  false
end

#requires_placeholder_type_specifiers? ⇒ Boolean

Whether type specifiers are required for prepared statement/bound variable argument placeholders (i.e. :bv__integer), false by default.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 41

def requires_placeholder_type_specifiers?
  false
end

#requires_sql_standard_datetimes? ⇒ Boolean

Whether the dataset requires SQL standard datetimes. False by default, as most allow strings with ISO 8601 format. Only for backwards compatibility, no longer used internally, do not use in new code.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 33

def requires_sql_standard_datetimes?
  # SEQUEL6: Remove
  false
end

#returning(*values) ⇒ Object

Modify the RETURNING clause, only supported on a few databases. If returning is used, instead of insert returning the autogenerated primary key or update/delete returning the number of modified rows, results are returned using fetch_rows.

DB[:items].returning # RETURNING *
DB[:items].returning(nil) # RETURNING NULL
DB[:items].returning(:id, :name) # RETURNING id, name

DB[:items].returning.insert(a: 1) do |hash|
  # hash for each row inserted, with values for all columns
end
DB[:items].returning.update(a: 1) do |hash|
  # hash for each row updated, with values for all columns
end
DB[:items].returning.delete(a: 1) do |hash|
  # hash for each row deleted, with values for all columns
end



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# File 'lib/sequel/dataset/query.rb', line 884

def returning(*values)
  if values.empty?
    return self if opts[:returning] == EMPTY_ARRAY
    cached_dataset(:_returning_ds) do
      raise Error, "RETURNING is not supported on #{db.database_type}" unless supports_returning?(:insert)
      clone(:returning=>EMPTY_ARRAY)
    end
  else
    raise Error, "RETURNING is not supported on #{db.database_type}" unless supports_returning?(:insert)
    clone(:returning=>values.freeze)
  end
end

#reverse(*order, &block) ⇒ Object

Returns a copy of the dataset with the order reversed. If no order is given, the existing order is inverted.

DB[:items].reverse(:id) # SELECT * FROM items ORDER BY id DESC
DB[:items].reverse{foo(bar)} # SELECT * FROM items ORDER BY foo(bar) DESC
DB[:items].order(:id).reverse # SELECT * FROM items ORDER BY id DESC
DB[:items].order(:id).reverse(Sequel.desc(:name)) # SELECT * FROM items ORDER BY name ASC



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# File 'lib/sequel/dataset/query.rb', line 904

def reverse(*order, &block)
  if order.empty? && !block
    cached_dataset(:_reverse_ds){order(*invert_order(@opts[:order]))}
  else
    virtual_row_columns(order, block)
    order(*invert_order(order.empty? ? @opts[:order] : order.freeze))
  end
end

#reverse_order(*order, &block) ⇒ Object

Alias of reverse



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# File 'lib/sequel/dataset/query.rb', line 914

def reverse_order(*order, &block)
  reverse(*order, &block)
end

#row_number_column ⇒ Object

The alias to use for the row_number column, used when emulating OFFSET support and for eager limit strategies



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# File 'lib/sequel/dataset/misc.rb', line 173

def row_number_column
  :x_sequel_row_number_x
end

#row_proc ⇒ Object

The row_proc for this database, should be any object that responds to call with a single hash argument and returns the object you want #each to return.



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# File 'lib/sequel/dataset/misc.rb', line 179

def row_proc
  @opts[:row_proc]
end

#schema_and_table(table_name, sch = nil) ⇒ Object

Split the schema information from the table, returning two strings, one for the schema and one for the table. The returned schema may be nil, but the table will always have a string value.

Note that this function does not handle tables with more than one level of qualification (e.g. database.schema.table on Microsoft SQL Server).



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# File 'lib/sequel/dataset/sql.rb', line 726

def schema_and_table(table_name, sch=nil)
  sch = sch.to_s if sch
  case table_name
  when Symbol
    s, t, _ = split_symbol(table_name)
    [s||sch, t]
  when SQL::QualifiedIdentifier
    [table_name.table.to_s, table_name.column.to_s]
  when SQL::Identifier
    [sch, table_name.value.to_s]
  when String
    [sch, table_name]
  else
    raise Error, 'table_name should be a Symbol, SQL::QualifiedIdentifier, SQL::Identifier, or String'
  end
end

#select(*columns, &block) ⇒ Object

Returns a copy of the dataset with the columns selected changed to the given columns. This also takes a virtual row block, similar to where.

DB[:items].select(:a) # SELECT a FROM items
DB[:items].select(:a, :b) # SELECT a, b FROM items
DB[:items].select{[a, sum(b)]} # SELECT a, sum(b) FROM items



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# File 'lib/sequel/dataset/query.rb', line 925

def select(*columns, &block)
  virtual_row_columns(columns, block)
  clone(:select => columns.freeze)
end

#select_all(*tables) ⇒ Object

Returns a copy of the dataset selecting the wildcard if no arguments are given. If arguments are given, treat them as tables and select all columns (using the wildcard) from each table.

DB[:items].select(:a).select_all # SELECT * FROM items
DB[:items].select_all(:items) # SELECT items.* FROM items
DB[:items].select_all(:items, :foo) # SELECT items.*, foo.* FROM items



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# File 'lib/sequel/dataset/query.rb', line 937

def select_all(*tables)
  if tables.empty?
    return self unless opts[:select]
    cached_dataset(:_select_all_ds){clone(:select => nil)}
  else
    select(*tables.map{|t| i, a = split_alias(t); a || i}.map!{|t| SQL::ColumnAll.new(t)}.freeze)
  end
end

#select_append(*columns, &block) ⇒ Object

Returns a copy of the dataset with the given columns added to the existing selected columns. If no columns are currently selected, it will select the columns given in addition to *.

DB[:items].select(:a).select(:b) # SELECT b FROM items
DB[:items].select(:a).select_append(:b) # SELECT a, b FROM items
DB[:items].select_append(:b) # SELECT *, b FROM items



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# File 'lib/sequel/dataset/query.rb', line 953

def select_append(*columns, &block)
  virtual_row_columns(columns, block)
  select(*(_current_select(true) + columns))
end

#select_group(*columns, &block) ⇒ Object

Set both the select and group clauses with the given columns. Column aliases may be supplied, and will be included in the select clause. This also takes a virtual row block similar to where.

DB[:items].select_group(:a, :b)
# SELECT a, b FROM items GROUP BY a, b

DB[:items].select_group(Sequel[:c].as(:a)){f(c2)}
# SELECT c AS a, f(c2) FROM items GROUP BY c, f(c2)



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# File 'lib/sequel/dataset/query.rb', line 967

def select_group(*columns, &block)
  virtual_row_columns(columns, block)
  select(*columns).group(*columns.map{|c| unaliased_identifier(c)})
end

#select_hash(key_column, value_column, opts = OPTS) ⇒ Object

Returns a hash with key_column values as keys and value_column values as values. Similar to as_hash, but only selects the columns given. Like as_hash, it accepts an optional :hash parameter, into which entries will be merged. 

DB[:table].select_hash(:id, :name)
# SELECT id, name FROM table
# => {1=>'a', 2=>'b', ...}

You can also provide an array of column names for either the key_column, the value column, or both:

DB[:table].select_hash([:id, :foo], [:name, :bar])
# SELECT id, foo, name, bar FROM table
# => {[1, 3]=>['a', 'c'], [2, 4]=>['b', 'd'], ...}

When using this method, you must be sure that each expression has an alias that Sequel can determine.



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# File 'lib/sequel/dataset/actions.rb', line 704

def select_hash(key_column, value_column, opts = OPTS)
  _select_hash(:as_hash, key_column, value_column, opts)
end

#select_hash_groups(key_column, value_column, opts = OPTS) ⇒ Object

Returns a hash with key_column values as keys and an array of value_column values. Similar to to_hash_groups, but only selects the columns given. Like to_hash_groups, it accepts an optional :hash parameter, into which entries will be merged. 

DB[:table].select_hash_groups(:name, :id)
# SELECT id, name FROM table
# => {'a'=>[1, 4, ...], 'b'=>[2, ...], ...}

You can also provide an array of column names for either the key_column, the value column, or both:

DB[:table].select_hash_groups([:first, :middle], [:last, :id])
# SELECT first, middle, last, id FROM table
# => {['a', 'b']=>[['c', 1], ['d', 2], ...], ...}

When using this method, you must be sure that each expression has an alias that Sequel can determine.



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# File 'lib/sequel/dataset/actions.rb', line 725

def select_hash_groups(key_column, value_column, opts = OPTS)
  _select_hash(:to_hash_groups, key_column, value_column, opts)
end

#select_map(column = nil, &block) ⇒ Object

Selects the column given (either as an argument or as a block), and returns an array of all values of that column in the dataset. If you give a block argument that returns an array with multiple entries, the contents of the resulting array are undefined. Raises an Error if called with both an argument and a block.

DB[:table].select_map(:id) # SELECT id FROM table
# => [3, 5, 8, 1, ...]

DB[:table].select_map{id * 2} # SELECT (id * 2) FROM table
# => [6, 10, 16, 2, ...]

You can also provide an array of column names:

DB[:table].select_map([:id, :name]) # SELECT id, name FROM table
# => [[1, 'A'], [2, 'B'], [3, 'C'], ...]

If you provide an array of expressions, you must be sure that each entry in the array has an alias that Sequel can determine.



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# File 'lib/sequel/dataset/actions.rb', line 748

def select_map(column=nil, &block)
  _select_map(column, false, &block)
end

#select_more(*columns, &block) ⇒ Object

Alias for select_append.



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# File 'lib/sequel/dataset/query.rb', line 973

def select_more(*columns, &block)
  select_append(*columns, &block)
end

#select_order_map(column = nil, &block) ⇒ Object

The same as select_map, but in addition orders the array by the column.

DB[:table].select_order_map(:id) # SELECT id FROM table ORDER BY id
# => [1, 2, 3, 4, ...]

DB[:table].select_order_map{id * 2} # SELECT (id * 2) FROM table ORDER BY (id * 2)
# => [2, 4, 6, 8, ...]

You can also provide an array of column names:

DB[:table].select_order_map([:id, :name]) # SELECT id, name FROM table ORDER BY id, name
# => [[1, 'A'], [2, 'B'], [3, 'C'], ...]

If you provide an array of expressions, you must be sure that each entry in the array has an alias that Sequel can determine.



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# File 'lib/sequel/dataset/actions.rb', line 767

def select_order_map(column=nil, &block)
  _select_map(column, true, &block)
end

#select_prepend(*columns, &block) ⇒ Object

Returns a copy of the dataset with the given columns added to the existing selected columns. If no columns are currently selected, it will select the columns given in addition to *.

DB[:items].select(:a).select(:b) # SELECT b FROM items
DB[:items].select(:a).select_prepend(:b) # SELECT b, a FROM items
DB[:items].select_prepend(:b) # SELECT b, * FROM items



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# File 'lib/sequel/dataset/query.rb', line 984

def select_prepend(*columns, &block)
  virtual_row_columns(columns, block)
  select(*(columns + _current_select(false)))
end

#server(servr) ⇒ Object

Set the server for this dataset to use. Used to pick a specific database shard to run a query against, or to override the default (where SELECT uses :read_only database and all other queries use the :default database). This method is always available but is only useful when database sharding is being used.

DB[:items].all # Uses the :read_only or :default server 
DB[:items].delete # Uses the :default server
DB[:items].server(:blah).delete # Uses the :blah server



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# File 'lib/sequel/dataset/query.rb', line 998

def server(servr)
  clone(:server=>servr)
end

#server?(server) ⇒ Boolean

If the database uses sharding and the current dataset has not had a server set, return a cloned dataset that uses the given server. Otherwise, return the receiver directly instead of returning a clone.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/query.rb', line 1005

def server?(server)
  if db.sharded? && !opts[:server]
    server(server)
  else
    self
  end
end

#set_graph_aliases(graph_aliases) ⇒ Object

This allows you to manually specify the graph aliases to use when using graph. You can use it to only select certain columns, and have those columns mapped to specific aliases in the result set. This is the equivalent of select for a graphed dataset, and must be used instead of select whenever graphing is used.

graph_aliases should be a hash with keys being symbols of column aliases, and values being either symbols or arrays with one to three elements. If the value is a symbol, it is assumed to be the same as a one element array containing that symbol. The first element of the array should be the table alias symbol. The second should be the actual column name symbol. If the array only has a single element the column name symbol will be assumed to be the same as the corresponding hash key. If the array has a third element, it is used as the value returned, instead of table_alias.column_name.

DB[:artists].graph(:albums, :artist_id: :id).
  set_graph_aliases(name: :artists,
                    album_name: [:albums, :name],
                    forty_two: [:albums, :fourtwo, 42]).first
# SELECT artists.name, albums.name AS album_name, 42 AS forty_two ...



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# File 'lib/sequel/dataset/graph.rb', line 244

def set_graph_aliases(graph_aliases)
  columns, graph_aliases = graph_alias_columns(graph_aliases)
  if graph = opts[:graph]
    select(*columns).clone(:graph => graph.merge(:column_aliases=>graph_aliases.freeze).freeze)
  else
    raise Error, "cannot call #set_graph_aliases on an ungraphed dataset"
  end
end

#single_record ⇒ Object

Limits the dataset to one record, and returns the first record in the dataset, or nil if the dataset has no records. Users should probably use first instead of this method. Example:

DB[:test].single_record # SELECT * FROM test LIMIT 1
# => {:column_name=>'value'}



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# File 'lib/sequel/dataset/actions.rb', line 777

def single_record
  _single_record_ds.single_record!
end

#single_record! ⇒ Object

Returns the first record in dataset, without limiting the dataset. Returns nil if the dataset has no records. Users should probably use first instead of this method. This should only be used if you know the dataset is already limited to a single record. This method may be desirable to use for performance reasons, as it does not clone the receiver. Example:

DB[:test].single_record! # SELECT * FROM test
# => {:column_name=>'value'}



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# File 'lib/sequel/dataset/actions.rb', line 789

def single_record!
  with_sql_first(select_sql)
end

#single_value ⇒ Object

Returns the first value of the first record in the dataset. Returns nil if dataset is empty. Users should generally use get instead of this method. Example:

DB[:test].single_value # SELECT * FROM test LIMIT 1
# => 'value'



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# File 'lib/sequel/dataset/actions.rb', line 799

def single_value
  single_value_ds.each do |r|
    r.each{|_, v| return v}
  end
  nil
end

#single_value! ⇒ Object

Returns the first value of the first record in the dataset, without limiting the dataset. Returns nil if the dataset is empty. Users should generally use get instead of this method. Should not be used on graphed datasets or datasets that have row_procs that don’t return hashes. This method may be desirable to use for performance reasons, as it does not clone the receiver.

DB[:test].single_value! # SELECT * FROM test
# => 'value'



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# File 'lib/sequel/dataset/actions.rb', line 814

def single_value!
  with_sql_single_value(select_sql)
end

#skip_limit_check ⇒ Object

Specify that the check for limits/offsets when updating/deleting be skipped for the dataset.



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# File 'lib/sequel/dataset/query.rb', line 1014

def skip_limit_check
  return self if opts[:skip_limit_check]
  cached_dataset(:_skip_limit_check_ds) do
    clone(:skip_limit_check=>true)
  end
end

#skip_locked ⇒ Object

Skip locked rows when returning results from this dataset.



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# File 'lib/sequel/dataset/query.rb', line 1022

def skip_locked
  return self if opts[:skip_locked]
  cached_dataset(:_skip_locked_ds) do
    raise(Error, 'This dataset does not support skipping locked rows') unless supports_skip_locked?
    clone(:skip_locked=>true)
  end
end

#split_alias(c) ⇒ Object

Splits a possible implicit alias in c, handling both SQL::AliasedExpressions and Symbols. Returns an array of two elements, with the first being the main expression, and the second being the alias.



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# File 'lib/sequel/dataset/misc.rb', line 186

def split_alias(c)
  case c
  when Symbol
    c_table, column, aliaz = split_symbol(c)
    [c_table ? SQL::QualifiedIdentifier.new(c_table, column.to_sym) : column.to_sym, aliaz]
  when SQL::AliasedExpression
    [c.expression, c.alias]
  when SQL::JoinClause
    [c.table, c.table_alias]
  else
    [c, nil]
  end
end

#split_qualifiers(table_name, *args) ⇒ Object

Splits table_name into an array of strings.

ds.split_qualifiers(:s) # ['s']
ds.split_qualifiers(Sequel[:t][:s]) # ['t', 's']
ds.split_qualifiers(Sequel[:d][:t][:s]) # ['d', 't', 's']
ds.split_qualifiers(Sequel.qualify(Sequel[:h][:d], Sequel[:t][:s])) # ['h', 'd', 't', 's']



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# File 'lib/sequel/dataset/sql.rb', line 749

def split_qualifiers(table_name, *args)
  case table_name
  when SQL::QualifiedIdentifier
    split_qualifiers(table_name.table, nil) + split_qualifiers(table_name.column, nil)
  else
    sch, table = schema_and_table(table_name, *args)
    sch ? [sch, table] : [table]
  end
end

#sql ⇒ Object

Same as select_sql, not aliased directly to make subclassing simpler.



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# File 'lib/sequel/dataset/sql.rb', line 176

def sql
  select_sql
end

#subscript_sql_append(sql, s) ⇒ Object

Append literalization of subscripts (SQL array accesses) to SQL string.



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# File 'lib/sequel/dataset/sql.rb', line 760

def subscript_sql_append(sql, s)
  case s.expression
  when Symbol, SQL::Subscript, SQL::Identifier, SQL::QualifiedIdentifier
    # nothing
  else
    wrap_expression = true
    sql << '('
  end
  literal_append(sql, s.expression)
  if wrap_expression
    sql << ')['
  else
    sql << '['
  end
  sub = s.sub
  if sub.length == 1 && (range = sub.first).is_a?(Range)
    literal_append(sql, range.begin)
    sql << ':'
    e = range.end
    e -= 1 if range.exclude_end? && e.is_a?(Integer)
    literal_append(sql, e)
  else
    expression_list_append(sql, s.sub)
  end
  sql << ']'
end

#sum(arg = (no_arg = true), &block) ⇒ Object

Returns the sum for the given column/expression. Uses a virtual row block if no column is given.

DB[:table].sum(:id) # SELECT sum(id) FROM table LIMIT 1
# => 55
DB[:table].sum{function(column)} # SELECT sum(function(column)) FROM table LIMIT 1
# => 10



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# File 'lib/sequel/dataset/actions.rb', line 825

def sum(arg=(no_arg = true), &block)
  arg = Sequel.virtual_row(&block) if no_arg
  _aggregate(:sum, arg)
end

#supports_cte?(type = :select) ⇒ Boolean

Whether the dataset supports common table expressions, false by default. If given, type can be :select, :insert, :update, or :delete, in which case it determines whether WITH is supported for the respective statement type.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 48

def supports_cte?(type=:select)
  false
end

#supports_cte_in_subqueries? ⇒ Boolean

Whether the dataset supports common table expressions in subqueries, false by default. If false, applies the WITH clause to the main query, which can cause issues if multiple WITH clauses use the same name.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 55

def supports_cte_in_subqueries?
  false
end

#supports_deleting_joins? ⇒ Boolean

Whether deleting from joined datasets is supported, false by default.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 60

def supports_deleting_joins?
  supports_modifying_joins?
end

#supports_derived_column_lists? ⇒ Boolean

Whether the database supports derived column lists (e.g. “table_expr AS table_alias(column_alias1, column_alias2, …)”), true by default.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 67

def supports_derived_column_lists?
  true
end

#supports_distinct_on? ⇒ Boolean

Whether the dataset supports or can emulate the DISTINCT ON clause, false by default.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 72

def supports_distinct_on?
  false
end

#supports_group_cube? ⇒ Boolean

Whether the dataset supports CUBE with GROUP BY, false by default.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 77

def supports_group_cube?
  false
end

#supports_group_rollup? ⇒ Boolean

Whether the dataset supports ROLLUP with GROUP BY, false by default.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 82

def supports_group_rollup?
  false
end

#supports_grouping_sets? ⇒ Boolean

Whether the dataset supports GROUPING SETS with GROUP BY, false by default.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 87

def supports_grouping_sets?
  false
end

#supports_insert_select? ⇒ Boolean

Whether this dataset supports the insert_select method for returning all columns values directly from an insert query, false by default.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 93

def supports_insert_select?
  supports_returning?(:insert)
end

#supports_intersect_except? ⇒ Boolean

Whether the dataset supports the INTERSECT and EXCEPT compound operations, true by default.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 98

def supports_intersect_except?
  true
end

#supports_intersect_except_all? ⇒ Boolean

Whether the dataset supports the INTERSECT ALL and EXCEPT ALL compound operations, true by default.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 103

def supports_intersect_except_all?
  true
end

#supports_is_true? ⇒ Boolean

Whether the dataset supports the IS TRUE syntax, true by default.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 108

def supports_is_true?
  true
end

#supports_join_using? ⇒ Boolean

Whether the dataset supports the JOIN table USING (column1, …) syntax, true by default. If false, support is emulated using JOIN table ON (table.column1 = other_table.column1).

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 114

def supports_join_using?
  true
end

#supports_lateral_subqueries? ⇒ Boolean

Whether the dataset supports LATERAL for subqueries in the FROM or JOIN clauses, false by default.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 119

def supports_lateral_subqueries?
  false
end

#supports_limits_in_correlated_subqueries? ⇒ Boolean

Whether limits are supported in correlated subqueries, true by default.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 124

def supports_limits_in_correlated_subqueries?
  true
end

#supports_merge? ⇒ Boolean

Whether the MERGE statement is supported, false by default.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 134

def supports_merge?
  false
end

#supports_modifying_joins? ⇒ Boolean

Whether modifying joined datasets is supported, false by default.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 139

def supports_modifying_joins?
  false
end

#supports_multiple_column_in? ⇒ Boolean

Whether the IN/NOT IN operators support multiple columns when an array of values is given, true by default.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 145

def supports_multiple_column_in?
  true
end

#supports_nowait? ⇒ Boolean

Whether the dataset supports skipping raising an error instead of waiting for locked rows when returning data, false by default.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 129

def supports_nowait?
  false
end

#supports_offsets_in_correlated_subqueries? ⇒ Boolean

Whether offsets are supported in correlated subqueries, true by default.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 150

def supports_offsets_in_correlated_subqueries?
  true
end

#supports_ordered_distinct_on? ⇒ Boolean

Whether the dataset supports or can fully emulate the DISTINCT ON clause, including respecting the ORDER BY clause, false by default.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 156

def supports_ordered_distinct_on?
  supports_distinct_on?
end

#supports_placeholder_literalizer? ⇒ Boolean

Whether placeholder literalizers are supported, true by default.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 161

def supports_placeholder_literalizer?
  true
end

#supports_regexp? ⇒ Boolean

Whether the dataset supports pattern matching by regular expressions, false by default.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 166

def supports_regexp?
  false
end

#supports_replace? ⇒ Boolean

Whether the dataset supports REPLACE syntax, false by default.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 171

def supports_replace?
  false
end

#supports_returning?(type) ⇒ Boolean

Whether the RETURNING clause is supported for the given type of query, false by default. type can be :insert, :update, or :delete.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 177

def supports_returning?(type)
  false
end

#supports_select_all_and_column? ⇒ Boolean

Whether the database supports SELECT *, column FROM table, true by default.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 187

def supports_select_all_and_column?
  true
end

#supports_skip_locked? ⇒ Boolean

Whether the dataset supports skipping locked rows when returning data, false by default.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 182

def supports_skip_locked?
  false
end

#supports_timestamp_timezones? ⇒ Boolean

Whether the dataset supports timezones in literal timestamps, false by default.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 194

def supports_timestamp_timezones?
  # SEQUEL6: Remove
  false
end

#supports_timestamp_usecs? ⇒ Boolean

Whether the dataset supports fractional seconds in literal timestamps, true by default.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 201

def supports_timestamp_usecs?
  true
end

#supports_updating_joins? ⇒ Boolean

Whether updating joined datasets is supported, false by default.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 206

def supports_updating_joins?
  supports_modifying_joins?
end

#supports_where_true? ⇒ Boolean

Whether the dataset supports WHERE TRUE (or WHERE 1 for databases that that use 1 for true), true by default.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 235

def supports_where_true?
  true
end

#supports_window_clause? ⇒ Boolean

Whether the dataset supports the WINDOW clause to define windows used by multiple window functions, false by default.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 212

def supports_window_clause?
  false
end

#supports_window_function_frame_option?(option) ⇒ Boolean

Whether the dataset supports the given window function option. True by default. This should only be called if supports_window_functions? is true. Possible options are :rows, :range, :groups, :offset, :exclude.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 224

def supports_window_function_frame_option?(option)
  case option
  when :rows, :range, :offset
    true
  else
    false
  end
end

#supports_window_functions? ⇒ Boolean

Whether the dataset supports window functions, false by default.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 217

def supports_window_functions?
  false
end

#to_hash(*a) ⇒ Object

Alias of as_hash for backwards compatibility.



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# File 'lib/sequel/dataset/actions.rb', line 882

def to_hash(*a)
  as_hash(*a)
end

#to_hash_groups(key_column, value_column = nil, opts = OPTS) ⇒ Object

Returns a hash with one column used as key and the values being an array of column values. If the value_column is not given or nil, uses the entire hash as the value.

DB[:table].to_hash_groups(:name, :id) # SELECT * FROM table
# {'Jim'=>[1, 4, 16, ...], 'Bob'=>[2], ...}

DB[:table].to_hash_groups(:name) # SELECT * FROM table
# {'Jim'=>[{:id=>1, :name=>'Jim'}, {:id=>4, :name=>'Jim'}, ...], 'Bob'=>[{:id=>2, :name=>'Bob'}], ...}

You can also provide an array of column names for either the key_column, the value column, or both:

DB[:table].to_hash_groups([:first, :middle], [:last, :id]) # SELECT * FROM table
# {['Jim', 'Bob']=>[['Smith', 1], ['Jackson', 4], ...], ...}

DB[:table].to_hash_groups([:first, :middle]) # SELECT * FROM table
# {['Jim', 'Bob']=>[{:id=>1, :first=>'Jim', :middle=>'Bob', :last=>'Smith'}, ...], ...}

Options:

:all

Use all instead of each to retrieve the objects

:hash

The object into which the values will be placed. If this is not given, an empty hash is used. This can be used to use a hash with a default value or default proc.



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# File 'lib/sequel/dataset/actions.rb', line 910

def to_hash_groups(key_column, value_column = nil, opts = OPTS)
  h = opts[:hash] || {}
  meth = opts[:all] ? :all : :each
  if value_column
    return naked.to_hash_groups(key_column, value_column, opts) if row_proc
    if value_column.is_a?(Array)
      if key_column.is_a?(Array)
        public_send(meth){|r| (h[r.values_at(*key_column)] ||= []) << r.values_at(*value_column)}
      else
        public_send(meth){|r| (h[r[key_column]] ||= []) << r.values_at(*value_column)}
      end
    else
      if key_column.is_a?(Array)
        public_send(meth){|r| (h[r.values_at(*key_column)] ||= []) << r[value_column]}
      else
        public_send(meth){|r| (h[r[key_column]] ||= []) << r[value_column]}
      end
    end
  elsif key_column.is_a?(Array)
    public_send(meth){|r| (h[key_column.map{|k| r[k]}] ||= []) << r}
  else
    public_send(meth){|r| (h[r[key_column]] ||= []) << r}
  end
  h
end

#truncate ⇒ Object

Truncates the dataset. Returns nil.

DB[:table].truncate # TRUNCATE table
# => nil



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# File 'lib/sequel/dataset/actions.rb', line 940

def truncate
  execute_ddl(truncate_sql)
end

#truncate_sql ⇒ Object

Returns a TRUNCATE SQL query string. See truncate

DB[:items].truncate_sql # => 'TRUNCATE items'



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# File 'lib/sequel/dataset/sql.rb', line 183

def truncate_sql
  if opts[:sql]
    static_sql(opts[:sql])
  else
    check_truncation_allowed!
    check_not_limited!(:truncate)
    raise(InvalidOperation, "Can't truncate filtered datasets") if opts[:where] || opts[:having]
    t = String.new
    source_list_append(t, opts[:from])
    _truncate_sql(t)
  end
end

#unfiltered ⇒ Object

Returns a copy of the dataset with no filters (HAVING or WHERE clause) applied.

DB[:items].group(:a).having(a: 1).where(:b).unfiltered
# SELECT * FROM items GROUP BY a



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# File 'lib/sequel/dataset/query.rb', line 1034

def unfiltered
  return self unless opts[:where] || opts[:having]
  cached_dataset(:_unfiltered_ds){clone(:where => nil, :having => nil)}
end

#ungraphed ⇒ Object

Remove the splitting of results into subhashes, and all metadata related to the current graph (if any).



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# File 'lib/sequel/dataset/graph.rb', line 255

def ungraphed
  return self unless opts[:graph]
  clone(:graph=>nil)
end

#ungrouped ⇒ Object

Returns a copy of the dataset with no grouping (GROUP or HAVING clause) applied.

DB[:items].group(:a).having(a: 1).where(:b).ungrouped
# SELECT * FROM items WHERE b



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# File 'lib/sequel/dataset/query.rb', line 1043

def ungrouped
  return self unless opts[:group] || opts[:having]
  cached_dataset(:_ungrouped_ds){clone(:group => nil, :having => nil)}
end

#union(dataset, opts = OPTS) ⇒ Object

Adds a UNION clause using a second dataset object. A UNION compound dataset returns all rows in either the current dataset or the given dataset. Options:

:alias

Use the given value as the from_self alias

:all

Set to true to use UNION ALL instead of UNION, so duplicate rows can occur

:from_self

Set to false to not wrap the returned dataset in a from_self, use with care.

DB[:items].union(DB[:other_items])
# SELECT * FROM (SELECT * FROM items UNION SELECT * FROM other_items) AS t1

DB[:items].union(DB[:other_items], all: true, from_self: false)
# SELECT * FROM items UNION ALL SELECT * FROM other_items

DB[:items].union(DB[:other_items], alias: :i)
# SELECT * FROM (SELECT * FROM items UNION SELECT * FROM other_items) AS i



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# File 'lib/sequel/dataset/query.rb', line 1064

def union(dataset, opts=OPTS)
  compound_clone(:union, dataset, opts)
end

#unlimited ⇒ Object

Returns a copy of the dataset with no limit or offset.

DB[:items].limit(10, 20).unlimited # SELECT * FROM items



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# File 'lib/sequel/dataset/query.rb', line 1071

def unlimited
  return self unless opts[:limit] || opts[:offset]
  cached_dataset(:_unlimited_ds){clone(:limit=>nil, :offset=>nil)}
end

#unordered ⇒ Object

Returns a copy of the dataset with no order.

DB[:items].order(:a).unordered # SELECT * FROM items



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# File 'lib/sequel/dataset/query.rb', line 1079

def unordered
  return self unless opts[:order]
  cached_dataset(:_unordered_ds){clone(:order=>nil)}
end

#unqualified_column_for(v) ⇒ Object

This returns an SQL::Identifier or SQL::AliasedExpression containing an SQL identifier that represents the unqualified column for the given value. The given value should be a Symbol, SQL::Identifier, SQL::QualifiedIdentifier, or SQL::AliasedExpression containing one of those. In other cases, this returns nil.



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# File 'lib/sequel/dataset/misc.rb', line 205

def unqualified_column_for(v)
  unless v.is_a?(String)
    _unqualified_column_for(v)
  end
end

#unused_table_alias(table_alias, used_aliases = []) ⇒ Object

Creates a unique table alias that hasn’t already been used in the dataset. table_alias can be any type of object accepted by alias_symbol. The symbol returned will be the implicit alias in the argument, possibly appended with “_N” if the implicit alias has already been used, where N is an integer starting at 0 and increasing until an unused one is found.

You can provide a second addition array argument containing symbols that should not be considered valid table aliases. The current aliases for the FROM and JOIN tables are automatically included in this array.

DB[:table].unused_table_alias(:t)
# => :t

DB[:table].unused_table_alias(:table)
# => :table_0

DB[:table, :table_0].unused_table_alias(:table)
# => :table_1

DB[:table, :table_0].unused_table_alias(:table, [:table_1, :table_2])
# => :table_3



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# File 'lib/sequel/dataset/misc.rb', line 233

def unused_table_alias(table_alias, used_aliases = [])
  table_alias = alias_symbol(table_alias)
  used_aliases += opts[:from].map{|t| alias_symbol(t)} if opts[:from]
  used_aliases += opts[:join].map{|j| j.table_alias ? alias_alias_symbol(j.table_alias) : alias_symbol(j.table)} if opts[:join]
  if used_aliases.include?(table_alias)
    i = 0
    while true
      ta = :"#{table_alias}_#{i}"
      return ta unless used_aliases.include?(ta)
      i += 1 
    end
  else
    table_alias
  end
end

#update(values = OPTS, &block) ⇒ Object

Updates values for the dataset. The returned value is the number of rows updated. values should be a hash where the keys are columns to set and values are the values to which to set the columns.

DB[:table].update(x: nil) # UPDATE table SET x = NULL
# => 10

DB[:table].update(x: Sequel[:x]+1, y: 0) # UPDATE table SET x = (x + 1), y = 0
# => 10

Some databases support using multiple tables in an UPDATE query. This requires multiple FROM tables (JOINs can also be used). As multiple FROM tables use an implicit CROSS JOIN, you should make sure your WHERE condition uses the appropriate filters for the FROM tables:

DB.from(:a, :b).join(:c, :d=>Sequel[:b][:e]).where{{a[:f]=>b[:g], a[:id]=>10}}.
  update(:f=>Sequel[:c][:h])
# UPDATE a
# SET f = c.h
# FROM b
# INNER JOIN c ON (c.d = b.e)
# WHERE ((a.f = b.g) AND (a.id = 10))



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# File 'lib/sequel/dataset/actions.rb', line 966

def update(values=OPTS, &block)
  sql = update_sql(values)
  if uses_returning?(:update)
    returning_fetch_rows(sql, &block)
  else
    execute_dui(sql)
  end
end

#update_sql(values = OPTS) ⇒ Object

Formats an UPDATE statement using the given values. See update.

DB[:items].update_sql(price: 100, category: 'software')
# => "UPDATE items SET price = 100, category = 'software'

Raises an Error if the dataset is grouped or includes more than one table.



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# File 'lib/sequel/dataset/sql.rb', line 203

def update_sql(values = OPTS)
  return static_sql(opts[:sql]) if opts[:sql]
  check_update_allowed!
  check_not_limited!(:update)

  case values
  when LiteralString
    # nothing
  when String
    raise Error, "plain string passed to Dataset#update is not supported, use Sequel.lit to use a literal string"
  end

  clone(:values=>values).send(:_update_sql)
end

#where(*cond, &block) ⇒ Object

Returns a copy of the dataset with the given WHERE conditions imposed upon it.

Accepts the following argument types:

Hash, Array of pairs

list of equality/inclusion expressions

Symbol

taken as a boolean column argument (e.g. WHERE active)

Sequel::SQL::BooleanExpression, Sequel::LiteralString

an existing condition expression, probably created using the Sequel expression filter DSL.

where also accepts a block, which should return one of the above argument types, and is treated the same way. This block yields a virtual row object, which is easy to use to create identifiers and functions. For more details on the virtual row support, see the “Virtual Rows” guide

If both a block and regular argument are provided, they get ANDed together.

Examples:

DB[:items].where(id: 3)
# SELECT * FROM items WHERE (id = 3)

DB[:items].where(Sequel.lit('price < ?', 100))
# SELECT * FROM items WHERE price < 100

DB[:items].where([[:id, [1,2,3]], [:id, 0..10]])
# SELECT * FROM items WHERE ((id IN (1, 2, 3)) AND ((id >= 0) AND (id <= 10)))

DB[:items].where(Sequel.lit('price < 100'))
# SELECT * FROM items WHERE price < 100

DB[:items].where(:active)
# SELECT * FROM items WHERE :active

DB[:items].where{price < 100}
# SELECT * FROM items WHERE (price < 100)

Multiple where calls can be chained for scoping:

software = dataset.where(category: 'software').where{price < 100}
# SELECT * FROM items WHERE ((category = 'software') AND (price < 100))

See the “Dataset Filtering” guide for more examples and details.



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# File 'lib/sequel/dataset/query.rb', line 1126

def where(*cond, &block)
  add_filter(:where, cond, &block)
end

#where_all(cond, &block) ⇒ Object

Return an array of all rows matching the given filter condition, also yielding each row to the given block. Basically the same as where(cond).all(&block), except it can be optimized to not create an intermediate dataset.

DB[:table].where_all(id: [1,2,3])
# SELECT * FROM table WHERE (id IN (1, 2, 3))



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# File 'lib/sequel/dataset/actions.rb', line 981

def where_all(cond, &block)
  if loader = _where_loader([cond], nil)
    loader.all(filter_expr(cond), &block)
  else
    where(cond).all(&block)
  end
end

#where_each(cond, &block) ⇒ Object

Iterate over all rows matching the given filter condition, yielding each row to the given block. Basically the same as where(cond).each(&block), except it can be optimized to not create an intermediate dataset.

DB[:table].where_each(id: [1,2,3]){|row| p row}
# SELECT * FROM table WHERE (id IN (1, 2, 3))



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# File 'lib/sequel/dataset/actions.rb', line 995

def where_each(cond, &block)
  if loader = _where_loader([cond], nil)
    loader.each(filter_expr(cond), &block)
  else
    where(cond).each(&block)
  end
end

#where_single_value(cond) ⇒ Object

Filter the datasets using the given filter condition, then return a single value. This assumes that the dataset has already been setup to limit the selection to a single column. Basically the same as where(cond).single_value, except it can be optimized to not create an intermediate dataset.

DB[:table].select(:name).where_single_value(id: 1)
# SELECT name FROM table WHERE (id = 1) LIMIT 1



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# File 'lib/sequel/dataset/actions.rb', line 1010

def where_single_value(cond)
  if loader = cached_where_placeholder_literalizer([cond], nil, :_where_single_value_loader) do |pl|
      single_value_ds.where(pl.arg)
    end

    loader.get(filter_expr(cond))
  else
    where(cond).single_value
  end
end

#window(name, opts) ⇒ Object

Return a clone of the dataset with an addition named window that can be referenced in window functions. See Sequel::SQL::Window for a list of options that can be passed in. Example:

DB[:items].window(:w, partition: :c1, order: :c2)
# SELECT * FROM items WINDOW w AS (PARTITION BY c1 ORDER BY c2)



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# File 'lib/sequel/dataset/query.rb', line 1136

def window(name, opts)
  clone(:window=>((@opts[:window]||EMPTY_ARRAY) + [[name, SQL::Window.new(opts)].freeze]).freeze)
end

#window_sql_append(sql, opts) ⇒ Object

Append literalization of windows (for window functions) to SQL string.

Raises:



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# File 'lib/sequel/dataset/sql.rb', line 788

def window_sql_append(sql, opts)
  raise(Error, 'This dataset does not support window functions') unless supports_window_functions?
  space = false
  space_s = ' '

  sql << '('

  if window = opts[:window]
    literal_append(sql, window)
    space = true
  end

  if part = opts[:partition]
    sql << space_s if space
    sql << "PARTITION BY "
    expression_list_append(sql, Array(part))
    space = true
  end

  if order = opts[:order]
    sql << space_s if space
    sql << "ORDER BY "
    expression_list_append(sql, Array(order))
    space = true
  end

  if frame = opts[:frame]
    sql << space_s if space

    if frame.is_a?(String)
      sql << frame
    else
      case frame
      when :all
        frame_type = :rows
        frame_start = :preceding
        frame_end = :following
      when :rows, :range, :groups
        frame_type = frame
        frame_start = :preceding
        frame_end = :current
      when Hash
        frame_type = frame[:type]
        unless frame_type == :rows || frame_type == :range || frame_type == :groups
          raise Error, "invalid window :frame :type option: #{frame_type.inspect}"
        end
        unless frame_start = frame[:start]
          raise Error, "invalid window :frame :start option: #{frame_start.inspect}"
        end
        frame_end = frame[:end]
        frame_exclude = frame[:exclude]
      else
        raise Error, "invalid window :frame option: #{frame.inspect}"
      end

      sql << frame_type.to_s.upcase << " "
      sql << 'BETWEEN ' if frame_end
      window_frame_boundary_sql_append(sql, frame_start, :preceding)
      if frame_end
        sql << " AND "
        window_frame_boundary_sql_append(sql, frame_end, :following)
      end

      if frame_exclude
        sql << " EXCLUDE "

        case frame_exclude
        when :current
          sql << "CURRENT ROW"
        when :group
          sql << "GROUP"
        when :ties
          sql << "TIES"
        when :no_others
          sql << "NO OTHERS"
        else
          raise Error, "invalid window :frame :exclude option: #{frame_exclude.inspect}"
        end
      end
    end
  end

  sql << ')'
end

#with(name, dataset, opts = OPTS) ⇒ Object

Add a common table expression (CTE) with the given name and a dataset that defines the CTE. A common table expression acts as an inline view for the query.

Options:

:args

Specify the arguments/columns for the CTE, should be an array of symbols.

:recursive

Specify that this is a recursive CTE

:materialized

Set to false to force inlining of the CTE, or true to force not inlining the CTE (PostgreSQL 12+/SQLite 3.35+).

DB[:items].with(:items, DB[:syx].where(Sequel[:name].like('A%')))
# WITH items AS (SELECT * FROM syx WHERE (name LIKE 'A%' ESCAPE '\')) SELECT * FROM items

Raises:



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# File 'lib/sequel/dataset/query.rb', line 1151

def with(name, dataset, opts=OPTS)
  raise(Error, 'This dataset does not support common table expressions') unless supports_cte?
  if hoist_cte?(dataset)
    s, ds = hoist_cte(dataset)
    s.with(name, ds, opts)
  else
    clone(:with=>((@opts[:with]||EMPTY_ARRAY) + [Hash[opts].merge!(:name=>name, :dataset=>dataset)]).freeze)
  end
end

#with_extend(*mods, &block) ⇒ Object

:nocov:



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# File 'lib/sequel/dataset/query.rb', line 1240

def with_extend(*mods, &block)
  c = Class.new(self.class)
  c.include(*mods) unless mods.empty?
  c.include(DatasetModule.new(&block)) if block
  o = c.freeze.allocate
  o.instance_variable_set(:@db, @db)
  o.instance_variable_set(:@opts, @opts)
  o.instance_variable_set(:@cache, {})
  if cols = cache_get(:_columns)
    o.send(:columns=, cols)
  end
  o.freeze
end

#with_quote_identifiers(v) ⇒ Object

Return a modified dataset with quote_identifiers set.



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# File 'lib/sequel/dataset/misc.rb', line 250

def with_quote_identifiers(v)
  clone(:quote_identifiers=>v, :skip_symbol_cache=>true)
end

#with_recursive(name, nonrecursive, recursive, opts = OPTS) ⇒ Object

Add a recursive common table expression (CTE) with the given name, a dataset that defines the nonrecursive part of the CTE, and a dataset that defines the recursive part of the CTE.

Options:

:args

Specify the arguments/columns for the CTE, should be an array of symbols.

:union_all

Set to false to use UNION instead of UNION ALL combining the nonrecursive and recursive parts.

PostgreSQL 14+ Options:

:cycle

Stop recursive searching when a cycle is detected. Includes two columns in the result of the CTE, a cycle column indicating whether a cycle was detected for the current row, and a path column for the path traversed to get to the current row. If given, must be a hash with the following keys:

:columns

(required) The column or array of columns to use to detect a cycle. If the value of these columns match columns already traversed, then a cycle is detected, and recursive searching will not traverse beyond the cycle (the CTE will include the row where the cycle was detected).

:cycle_column

The name of the cycle column in the output, defaults to :is_cycle.

:cycle_value

The value of the cycle column in the output if the current row was detected as a cycle, defaults to true.

:noncycle_value

The value of the cycle column in the output if the current row was not detected as a cycle, defaults to false. Only respected if :cycle_value is given.

:path_column

The name of the path column in the output, defaults to :path.

:search

Include an order column in the result of the CTE that allows for breadth or depth first searching. If given, must be a hash with the following keys:

:by

(required) The column or array of columns to search by.

:order_column

The name of the order column in the output, defaults to :ordercol.

:type

Set to :breadth to use breadth-first searching (depth-first searching is the default).

DB[:t].with_recursive(:t,
  DB[:i1].select(:id, :parent_id).where(parent_id: nil),
  DB[:i1].join(:t, id: :parent_id).select(Sequel[:i1][:id], Sequel[:i1][:parent_id]),
  args: [:id, :parent_id])

# WITH RECURSIVE t(id, parent_id) AS (
#   SELECT id, parent_id FROM i1 WHERE (parent_id IS NULL)
#   UNION ALL
#   SELECT i1.id, i1.parent_id FROM i1 INNER JOIN t ON (t.id = i1.parent_id)
# ) SELECT * FROM t

DB[:t].with_recursive(:t,
  DB[:i1].where(parent_id: nil),
  DB[:i1].join(:t, id: :parent_id).select_all(:i1),
  search: {by: :id, type: :breadth},
  cycle: {columns: :id, cycle_value: 1, noncycle_value: 2})

# WITH RECURSIVE t AS (
#     SELECT * FROM i1 WHERE (parent_id IS NULL)
#     UNION ALL
#     (SELECT i1.* FROM i1 INNER JOIN t ON (t.id = i1.parent_id))
#   )
#   SEARCH BREADTH FIRST BY id SET ordercol
#   CYCLE id SET is_cycle TO 1 DEFAULT 2 USING path
# SELECT * FROM t

Raises:



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# File 'lib/sequel/dataset/query.rb', line 1217

def with_recursive(name, nonrecursive, recursive, opts=OPTS)
  raise(Error, 'This dataset does not support common table expressions') unless supports_cte?
  if hoist_cte?(nonrecursive)
    s, ds = hoist_cte(nonrecursive)
    s.with_recursive(name, ds, recursive, opts)
  elsif hoist_cte?(recursive)
    s, ds = hoist_cte(recursive)
    s.with_recursive(name, nonrecursive, ds, opts)
  else
    clone(:with=>((@opts[:with]||EMPTY_ARRAY) + [Hash[opts].merge!(:recursive=>true, :name=>name, :dataset=>nonrecursive.union(recursive, {:all=>opts[:union_all] != false, :from_self=>false}))]).freeze)
  end
end

#with_row_proc(callable) ⇒ Object

Returns a cloned dataset with the given row_proc.

ds = DB[:items]
ds.all # => [{:id=>2}]
ds.with_row_proc(:invert.to_proc).all # => [{2=>:id}]



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# File 'lib/sequel/dataset/query.rb', line 1269

def with_row_proc(callable)
  clone(:row_proc=>callable)
end

#with_sql(sql, *args) ⇒ Object

Returns a copy of the dataset with the static SQL used. This is useful if you want to keep the same row_proc/graph, but change the SQL used to custom SQL.

DB[:items].with_sql('SELECT * FROM foo') # SELECT * FROM foo

You can use placeholders in your SQL and provide arguments for those placeholders:

DB[:items].with_sql('SELECT ? FROM foo', 1) # SELECT 1 FROM foo

You can also provide a method name and arguments to call to get the SQL:

DB[:items].with_sql(:insert_sql, b: 1) # INSERT INTO items (b) VALUES (1)

Note that datasets that specify custom SQL using this method will generally ignore future dataset methods that modify the SQL used, as specifying custom SQL overrides Sequel’s SQL generator. You should probably limit yourself to the following dataset methods when using this method, or use the implicit_subquery extension:

  • each

  • all

  • single_record (if only one record could be returned)

  • single_value (if only one record could be returned, and a single column is selected)

  • map

  • as_hash

  • to_hash

  • to_hash_groups

  • delete (if a DELETE statement)

  • update (if an UPDATE statement, with no arguments)

  • insert (if an INSERT statement, with no arguments)

  • truncate (if a TRUNCATE statement, with no arguments)



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# File 'lib/sequel/dataset/query.rb', line 1303

def with_sql(sql, *args)
  if sql.is_a?(Symbol)
    sql = public_send(sql, *args)
  else
    sql = SQL::PlaceholderLiteralString.new(sql, args) unless args.empty?
  end
  clone(:sql=>sql)
end

#with_sql_all(sql, &block) ⇒ Object

Run the given SQL and return an array of all rows. If a block is given, each row is yielded to the block after all rows are loaded. See with_sql_each.



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# File 'lib/sequel/dataset/actions.rb', line 1023

def with_sql_all(sql, &block)
  _all(block){|a| with_sql_each(sql){|r| a << r}}
end

#with_sql_delete(sql) ⇒ Object Also known as: with_sql_update

Execute the given SQL and return the number of rows deleted. This exists solely as an optimization, replacing with_sql(sql).delete. It’s significantly faster as it does not require cloning the current dataset.



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# File 'lib/sequel/dataset/actions.rb', line 1030

def with_sql_delete(sql)
  execute_dui(sql)
end

#with_sql_each(sql) ⇒ Object

Run the given SQL and yield each returned row to the block.



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# File 'lib/sequel/dataset/actions.rb', line 1036

def with_sql_each(sql)
  if rp = row_proc
    _with_sql_dataset.fetch_rows(sql){|r| yield rp.call(r)}
  else
    _with_sql_dataset.fetch_rows(sql){|r| yield r}
  end
  self
end

#with_sql_first(sql) ⇒ Object

Run the given SQL and return the first row, or nil if no rows were returned. See with_sql_each.



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# File 'lib/sequel/dataset/actions.rb', line 1047

def with_sql_first(sql)
  with_sql_each(sql){|r| return r}
  nil
end

#with_sql_insert(sql) ⇒ Object

Execute the given SQL and (on most databases) return the primary key of the inserted row.



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# File 'lib/sequel/dataset/actions.rb', line 1063

def with_sql_insert(sql)
  execute_insert(sql)
end

#with_sql_single_value(sql) ⇒ Object

Run the given SQL and return the first value in the first row, or nil if no rows were returned. For this to make sense, the SQL given should select only a single value. See with_sql_each.



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# File 'lib/sequel/dataset/actions.rb', line 1055

def with_sql_single_value(sql)
  if r = with_sql_first(sql)
    r.each{|_, v| return v}
  end
end