Class: Sequel::Dataset

Inherits:
Object show all
Includes:
Enumerable
Defined in:
lib/sequel_core/dataset.rb,
lib/sequel_core/dataset/sql.rb,
lib/sequel_core/object_graph.rb,
lib/sequel_core/dataset/query.rb,
lib/sequel_core/dataset/schema.rb,
lib/sequel_core/dataset/callback.rb,
lib/sequel_core/dataset/pagination.rb,
lib/sequel_core/dataset/convenience.rb,
lib/sequel_core/dataset/prepared_statements.rb

Overview

A Dataset represents a view of a the data in a database, constrained by specific parameters such as filtering conditions, order, etc. Datasets can be used to create, retrieve, update and delete records.

Query results are always retrieved on demand, so a dataset can be kept around and reused indefinitely:

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

In order to provide this functionality, dataset methods such as where, select, order, etc. return modified copies of the dataset, so you can use different datasets to access data:

posts = DB[:posts]
davids_posts = posts.filter(:author => 'david')
old_posts = posts.filter('stamp < ?', Date.today - 7)

Datasets are Enumerable objects, so they can be manipulated using any of the Enumerable methods, such as map, inject, etc.

Methods added via metaprogramming

Some methods are added via metaprogramming:

  • ! methods - These methods are the same as their non-! counterparts, but they modify the receiver instead of returning a modified copy of the dataset.

  • inner_join, full_outer_join, right_outer_join, left_outer_join - This methods are shortcuts to join_table with the join type already specified.

Defined Under Namespace

Modules: ArgumentMapper, Pagination, PreparedStatementMethods, QueryBlockCopy, UnnumberedArgumentMapper

Constant Summary collapse

COLUMN_CHANGE_OPTS =

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

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

Array of all subclasses of Dataset

[]
MUTATION_METHODS =

All methods that should have a ! method added that modifies the receiver.

%w'and distinct exclude exists filter from from_self full_outer_join graph
group group_and_count group_by having inner_join intersect invert join
left_outer_join limit naked or order order_by order_more paginate query reject
reverse reverse_order right_outer_join select select_all select_more
set_defaults set_graph_aliases set_model set_overrides sort sort_by
unfiltered union unordered where'.collect{|x| x.to_sym}
NOTIMPL_MSG = 
"This method must be overridden in Sequel adapters".freeze
STOCK_TRANSFORMS = 
{
  :marshal => [
    # for backwards-compatibility we support also non-base64-encoded values.
    proc {|v| Marshal.load(v.unpack('m')[0]) rescue Marshal.load(v)}, 
    proc {|v| [Marshal.dump(v)].pack('m')}
  ],
  :yaml => [
    proc {|v| YAML.load v if v}, 
    proc {|v| v.to_yaml}
  ]
}
AND_SEPARATOR = 
" AND ".freeze
BOOL_FALSE = 
"'f'".freeze
BOOL_TRUE = 
"'t'".freeze
COLUMN_REF_RE1 = 
/\A([\w ]+)__([\w ]+)___([\w ]+)\z/.freeze
COLUMN_REF_RE2 = 
/\A([\w ]+)___([\w ]+)\z/.freeze
COLUMN_REF_RE3 = 
/\A([\w ]+)__([\w ]+)\z/.freeze
COUNT_FROM_SELF_OPTS = 
[:distinct, :group, :sql, :limit]
DATE_FORMAT = 
"DATE '%Y-%m-%d'".freeze
N_ARITY_OPERATORS = 
::Sequel::SQL::ComplexExpression::N_ARITY_OPERATORS
NULL = 
"NULL".freeze
QUESTION_MARK = 
'?'.freeze
STOCK_COUNT_OPTS = 
{:select => ["COUNT(*)".lit], :order => nil}.freeze
TIMESTAMP_FORMAT = 
"TIMESTAMP '%Y-%m-%d %H:%M:%S'".freeze
TWO_ARITY_OPERATORS = 
::Sequel::SQL::ComplexExpression::TWO_ARITY_OPERATORS
WILDCARD = 
'*'.freeze
COMMA_SEPARATOR = 
', '.freeze
COUNT_OF_ALL_AS_COUNT = 
:count['*'.lit].as(:count)
PREPARED_ARG_PLACEHOLDER = 
'?'.lit.freeze

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Enumerable

#send_each

Constructor Details

#initialize(db, opts = nil) ⇒ Dataset

Constructs a new instance of a dataset with an associated database and options. Datasets are usually constructed by invoking Database methods:

DB[:posts]

Or:

DB.dataset # the returned dataset is blank

Sequel::Dataset is an abstract class that is not useful by itself. Each database adaptor should provide a descendant class of Sequel::Dataset.



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# File 'lib/sequel_core/dataset.rb', line 96

def initialize(db, opts = nil)
  @db = db
  @quote_identifiers = db.quote_identifiers? if db.respond_to?(:quote_identifiers?)
  @opts = opts || {}
  @row_proc = nil
  @transform = nil
end

Instance Attribute Details

#db ⇒ Object

The database that corresponds to this dataset



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# File 'lib/sequel_core/dataset.rb', line 72

def db
  @db
end

#opts ⇒ Object

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



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# File 'lib/sequel_core/dataset.rb', line 75

def opts
  @opts
end

#quote_identifiers=(value) ⇒ Object (writeonly)

Whether to quote identifiers for this dataset



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# File 'lib/sequel_core/dataset.rb', line 83

def quote_identifiers=(value)
  @quote_identifiers = value
end

#row_proc ⇒ Object

The row_proc for this database, should be a Proc that takes a single hash argument and returns the object you want to fetch_rows to return.



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# File 'lib/sequel_core/dataset.rb', line 80

def row_proc
  @row_proc
end

Class Method Details

.dataset_classes ⇒ Object

The array of dataset subclasses.



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# File 'lib/sequel_core/dataset.rb', line 107

def self.dataset_classes
  DATASET_CLASSES
end

.def_mutation_method(*meths) ⇒ Object

Setup mutation (e.g. filter!) methods. These operate the same as the non-! methods, but replace the options of the current dataset with the options of the resulting dataset.



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# File 'lib/sequel_core/dataset.rb', line 114

def self.def_mutation_method(*meths)
  meths.each do |meth|
    class_eval("def #{meth}!(*args, &block); mutation_method(:#{meth}, *args, &block) end")
  end
end

.inherited(c) ⇒ Object

Add the subclass to the array of subclasses.



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# File 'lib/sequel_core/dataset.rb', line 121

def self.inherited(c)
  DATASET_CLASSES << c
end

Instance Method Details

#<<(*args) ⇒ Object

Alias for insert, but not aliased directly so subclasses don’t have to override both methods.



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# File 'lib/sequel_core/dataset.rb', line 129

def <<(*args)
  insert(*args)
end

#[](*conditions) ⇒ Object

Returns the first record matching the conditions.



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# File 'lib/sequel_core/dataset/convenience.rb', line 7

def [](*conditions)
  first(*conditions)
end

#[]=(conditions, values) ⇒ Object

Update all records matching the conditions with the values specified.



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# File 'lib/sequel_core/dataset/convenience.rb', line 13

def []=(conditions, values)
  filter(conditions).update(values)
end

#aliased_expression_sql(ae) ⇒ Object

SQL fragment for the aliased expression



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# File 'lib/sequel_core/dataset/sql.rb', line 28

def aliased_expression_sql(ae)
  as_sql(literal(ae.expression), ae.aliaz)
end

#all(opts = nil, &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.



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# File 'lib/sequel_core/dataset.rb', line 141

def all(opts = nil, &block)
  a = []
  each(opts) {|r| a << r}
  post_load(a)
  a.each(&block) if block
  a
end

#and(*cond, &block) ⇒ Object

Adds an further filter to an existing filter using AND. If no filter exists an error is raised. This method is identical to #filter except it expects an existing filter.

Raises:



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

def and(*cond, &block)
  raise(Error::NoExistingFilter, "No existing filter found.") unless @opts[:having] || @opts[:where]
  filter(*cond, &block)
end

#as(aliaz) ⇒ Object

Return the dataset as a column with the given alias, so it can be used in the SELECT clause. This dataset should result in a single row and a single column.



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# File 'lib/sequel_core/dataset.rb', line 135

def as(aliaz)
  ::Sequel::SQL::AliasedExpression.new(self, aliaz)
end

#avg(column) ⇒ Object

Returns the average value for the given column.



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# File 'lib/sequel_core/dataset/convenience.rb', line 18

def avg(column)
  get(:avg[column])
end

#call(type, bind_variables = {}, values = nil) ⇒ Object

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



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# File 'lib/sequel_core/dataset/prepared_statements.rb', line 183

def call(type, bind_variables={}, values=nil)
  to_prepared_statement(type, values).call(bind_variables)
end

#case_expression_sql(ce) ⇒ Object

SQL fragment for specifying given CaseExpression.



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# File 'lib/sequel_core/dataset/sql.rb', line 33

def case_expression_sql(ce)
  sql = '(CASE '
  sql << "#{literal(ce.expression)} " if ce.expression
  ce.conditions.collect{ |c,r|
    sql << "WHEN #{literal(c)} THEN #{literal(r)} "
  }
  sql << "ELSE #{literal(ce.default)} END)"
end

#clone(opts = {}) ⇒ Object

Returns a new clone of the dataset with with the given options merged. If the options changed include options in COLUMN_CHANGE_OPTS, the cached columns are deleted.



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# File 'lib/sequel_core/dataset.rb', line 152

def clone(opts = {})
  c = super()
  c.opts = @opts.merge(opts)
  c.instance_variable_set(:@columns, nil) if opts.keys.any?{|o| COLUMN_CHANGE_OPTS.include?(o)}
  c
end

#column_all_sql(ca) ⇒ Object

SQL fragment for specifying all columns in a given table.



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# File 'lib/sequel_core/dataset/sql.rb', line 43

def column_all_sql(ca)
  "#{quote_identifier(ca.table)}.*"
end

#columns ⇒ Object

Returns the columns in the result set in their true order. If the columns are currently cached, returns the cached value. Otherwise, a SELECT query is performed to get a single row. Adapters are expected to fill the columns cache with the column information when a query is performed. If the dataset does not have any rows, this will be an empty array. If you are looking for all columns for a single table, see Schema::SQL#schema.



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# File 'lib/sequel_core/dataset.rb', line 165

def columns
  return @columns if @columns
  ds = unfiltered.unordered.clone(:distinct => nil)
  ds.single_record
  @columns = ds.instance_variable_get(:@columns)
  @columns || []
end

#columns! ⇒ Object

Remove the cached list of columns and do a SELECT query to find the columns.



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# File 'lib/sequel_core/dataset.rb', line 175

def columns!
  @columns = nil
  columns
end

#complex_expression_sql(op, args) ⇒ Object

SQL fragment for complex expressions



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# File 'lib/sequel_core/dataset/sql.rb', line 48

def complex_expression_sql(op, args)
  case op
  when *TWO_ARITY_OPERATORS
    "(#{literal(args.at(0))} #{op} #{literal(args.at(1))})"
  when *N_ARITY_OPERATORS
    "(#{args.collect{|a| literal(a)}.join(" #{op} ")})"
  when :NOT
    "NOT #{literal(args.at(0))}"
  when :NOOP
    literal(args.at(0))
  when :'B~'
    "~#{literal(args.at(0))}"
  else
    raise(Sequel::Error, "invalid operator #{op}")
  end
end

#count ⇒ Object Also known as: size

Returns the number of records in the dataset.



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# File 'lib/sequel_core/dataset/sql.rb', line 66

def count
  options_overlap(COUNT_FROM_SELF_OPTS) ? from_self.count : single_value(STOCK_COUNT_OPTS).to_i
end

#create_or_replace_view(name) ⇒ Object

Creates or replaces a view in the database with the given named based on the current dataset.



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# File 'lib/sequel_core/dataset/schema.rb', line 11

def create_or_replace_view(name)
  @db.create_or_replace_view(name, self)
end

#create_view(name) ⇒ Object

Creates a view in the database with the given named based on the current dataset.



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# File 'lib/sequel_core/dataset/schema.rb', line 5

def create_view(name)
  @db.create_view(name, self)
end

#def_mutation_method(*meths) ⇒ Object

Add a mutation method to this dataset instance.



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# File 'lib/sequel_core/dataset.rb', line 181

def def_mutation_method(*meths)
  meths.each do |meth|
    instance_eval("def #{meth}!(*args, &block); mutation_method(:#{meth}, *args, &block) end")
  end
end

#delete(*args) ⇒ Object

Deletes the records in the dataset. The returned value is generally the number of records deleted, but that is adapter dependent.



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# File 'lib/sequel_core/dataset.rb', line 189

def delete(*args)
  execute_dui(delete_sql(*args))
end

#delete_sql(opts = nil) ⇒ Object

Formats a DELETE statement using the given options and dataset options.

dataset.filter(:price >= 100).delete_sql #=>
  "DELETE FROM items WHERE (price >= 100)"



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# File 'lib/sequel_core/dataset/sql.rb', line 75

def delete_sql(opts = nil)
  opts = opts ? @opts.merge(opts) : @opts

  if sql = opts[:sql]
    return sql
  end

  if opts[:group]
    raise Error::InvalidOperation, "Grouped datasets cannot be deleted from"
  elsif opts[:from].is_a?(Array) && opts[:from].size > 1
    raise Error::InvalidOperation, "Joined datasets cannot be deleted from"
  end

  sql = "DELETE FROM #{source_list(opts[:from])}"

  if where = opts[:where]
    sql << " WHERE #{literal(where)}"
  end

  sql
end

#each(opts = nil, &block) ⇒ Object

Iterates over the records in the dataset.



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# File 'lib/sequel_core/dataset.rb', line 194

def each(opts = nil, &block)
  if @opts[:graph] and !(opts && opts[:graph] == false)
    graph_each(opts, &block)
  else
    row_proc = @row_proc unless opts && opts[:naked]
    transform = @transform
    fetch_rows(select_sql(opts)) do |r|
      r = transform_load(r) if transform
      r = row_proc[r] if row_proc
      yield r
    end
  end
  self
end

#each_page(page_size, &block) ⇒ Object

Yields a paginated dataset for each page and returns the receiver. Does a count to find the total number of records for this dataset.

Raises:



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# File 'lib/sequel_core/dataset/pagination.rb', line 16

def each_page(page_size, &block)
  raise(Error, "You cannot paginate a dataset that already has a limit") if @opts[:limit]
  record_count = count
  total_pages = (record_count / page_size.to_f).ceil
  (1..total_pages).each{|page_no| yield paginate(page_no, page_size, record_count)}
  self
end

#empty? ⇒ Boolean

Returns true if no records exists in the dataset

Returns:

  • (Boolean) 


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# File 'lib/sequel_core/dataset/convenience.rb', line 23

def empty?
  get(1).nil?
end

#except(dataset, all = false) ⇒ Object

Adds an EXCEPT clause using a second dataset object. If all is true the clause used is EXCEPT ALL, which may return duplicate rows.

DB[:items].except(DB[:other_items]).sql
#=> "SELECT * FROM items EXCEPT SELECT * FROM other_items"



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# File 'lib/sequel_core/dataset/sql.rb', line 102

def except(dataset, all = false)
  clone(:except => dataset, :except_all => all)
end

#exclude(*cond, &block) ⇒ Object

Performs the inverse of Dataset#filter.

dataset.exclude(:category => 'software').sql #=>
  "SELECT * FROM items WHERE (category != 'software')"



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# File 'lib/sequel_core/dataset/sql.rb', line 110

def exclude(*cond, &block)
  clause = (@opts[:having] ? :having : :where)
  cond = cond.first if cond.size == 1
  cond = cond.sql_or if (Hash === cond) || ((Array === cond) && (cond.all_two_pairs?))
  cond = filter_expr(cond, &block)
  cond = SQL::BooleanExpression.invert(cond)
  cond = SQL::BooleanExpression.new(:AND, @opts[clause], cond) if @opts[clause]
  clone(clause => cond)
end

#exists(opts = nil) ⇒ Object

Returns an EXISTS clause for the dataset.

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



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# File 'lib/sequel_core/dataset/sql.rb', line 124

def exists(opts = nil)
  "EXISTS (#{select_sql(opts)})"
end

#fetch_rows(sql, &block) ⇒ Object

Executes a select query and fetches records, passing each record to the supplied block. The yielded records are generally hashes with symbol keys, but that is adapter dependent.

Raises:

  • (NotImplementedError) 


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# File 'lib/sequel_core/dataset.rb', line 212

def fetch_rows(sql, &block)
  raise NotImplementedError, NOTIMPL_MSG
end

#filter(*cond, &block) ⇒ Object Also known as: where

Returns a copy of the dataset with the given conditions imposed upon it.

If the query has been grouped, then the conditions are imposed in the HAVING clause. If not, then they are imposed in the WHERE clause. Filter

filter accepts the following argument types:

  • Hash - list of equality expressions

  • Array - depends:

    • If first member is a string, assumes the rest of the arguments are parameters and interpolates them into the string.

    • If all members are arrays of length two, treats the same way as a hash, except it allows for duplicate keys to be specified.

  • String - taken literally

  • Symbol - taken as a boolean column argument (e.g. WHERE active)

  • Sequel::SQL::BooleanExpression - an existing condition expression, probably created using the Sequel blockless filter DSL.

filter also takes a block, which should return one of the above argument types, and is treated the same way. If both a block and regular argument are provided, they get ANDed together.

Examples:

dataset.filter(:id => 3).sql #=>
  "SELECT * FROM items WHERE (id = 3)"
dataset.filter('price < ?', 100).sql #=>
  "SELECT * FROM items WHERE price < 100"
dataset.filter([[:id, (1,2,3)], [:id, 0..10]]).sql #=>
  "SELECT * FROM items WHERE ((id IN (1, 2, 3)) AND ((id >= 0) AND (id <= 10)))"
dataset.filter('price < 100').sql #=>
  "SELECT * FROM items WHERE price < 100"
dataset.filter(:active).sql #=>
  "SELECT * FROM items WHERE :active
dataset.filter(:price < 100).sql #=>
  "SELECT * FROM items WHERE (price < 100)"

Multiple filter calls can be chained for scoping:

software = dataset.filter(:category => 'software')
software.filter(price < 100).sql #=>
  "SELECT * FROM items WHERE ((category = 'software') AND (price < 100))"

See doc/dataset_filters.rdoc for more examples and details.



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# File 'lib/sequel_core/dataset/sql.rb', line 172

def filter(*cond, &block)
  clause = (@opts[:having] ? :having : :where)
  cond = cond.first if cond.size == 1
  cond = transform_save(cond) if @transform if cond.is_a?(Hash)
  cond = filter_expr(cond, &block)
  cond = SQL::BooleanExpression.new(:AND, @opts[clause], cond) if @opts[clause] && !@opts[clause].blank?
  clone(clause => cond)
end

#first(*args, &block) ⇒ Object

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

Examples:

ds.first => {:id=>7}
ds.first(2) => [{:id=>6}, {:id=>4}]
ds.order(:id).first(2) => [{:id=>1}, {:id=>2}]
ds.first(:id=>2) => {:id=>2}
ds.first("id = 3") => {:id=>3}
ds.first("id = ?", 4) => {:id=>4}
ds.first{:id > 2} => {:id=>5}
ds.order(:id).first{:id > 2} => {:id=>3}
ds.first{:id > 2} => {:id=>5}
ds.first("id > ?", 4){:id < 6) => {:id=>5}
ds.order(:id).first(2){:id < 2} => [{:id=>1}]



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# File 'lib/sequel_core/dataset/convenience.rb', line 48

def first(*args, &block)
  ds = block ? filter(&block) : self

  if args.empty?
    ds.single_record
  else
    args = (args.size == 1) ? args.first : args
    if Integer === args
      ds.limit(args).all
    else
      ds.filter(args).single_record
    end
  end
end

#first_source ⇒ 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 actual table name, not the alias.



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# File 'lib/sequel_core/dataset/sql.rb', line 185

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

#from(*source) ⇒ Object

Returns a copy of the dataset with the source changed.



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# File 'lib/sequel_core/dataset/sql.rb', line 202

def from(*source)
  clone(:from => source)
end

#from_self ⇒ Object

Returns a dataset selecting from the current dataset.

ds = DB[:items].order(:name)
ds.sql #=> "SELECT * FROM items ORDER BY name"
ds.from_self.sql #=> "SELECT * FROM (SELECT * FROM items ORDER BY name)"



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# File 'lib/sequel_core/dataset/sql.rb', line 211

def from_self
  fs = {}
  @opts.keys.each{|k| fs[k] = nil} 
  fs[:from] = [self]
  clone(fs)
end

#function_sql(f) ⇒ Object

SQL fragment specifying an SQL function call



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# File 'lib/sequel_core/dataset/sql.rb', line 219

def function_sql(f)
  args = f.args
  "#{f.f}#{args.empty? ? '()' : literal(args)}"
end

#get(column) ⇒ Object

Return the column value for the first matching record in the dataset.



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# File 'lib/sequel_core/dataset/convenience.rb', line 64

def get(column)
  select(column).single_value
end

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

Allows you to join multiple datasets/tables and have the result set split into component tables.

This differs from the usual usage of join, which returns the result set as a single hash. For example:

# CREATE TABLE artists (id INTEGER, name TEXT);
# CREATE TABLE albums (id INTEGER, name TEXT, artist_id INTEGER);
DB[:artists].left_outer_join(:albums, :artist_id=>:id).first
=> {:id=>(albums.id||artists.id), :name=>(albums.name||artist.names), :artist_id=>albums.artist_id}
DB[:artists].graph(:albums, :artist_id=>:id).first
=> {:artists=>{:id=>artists.id, :name=>artists.name}, :albums=>{:id=>albums.id, :name=>albums.name, :artist_id=>albums.artist_id}}

Using a join such as left_outer_join, the attribute names that are shared between the tables are combined in the single return hash. You can get around that by using .select with correct aliases for all of the columns, but it is simpler to use graph and have the result set split for you. In addition, graph respects any row_proc or transform attributes of the current dataset and the datasets you use with graph.

If you are graphing a table and all columns for that table are nil, this indicates that no matching rows existed in the table, so graph will return nil instead of a hash with all nil values:

# If the artist doesn't have any albums
DB[:artists].graph(:albums, :artist_id=>:id).first
=> {:artists=>{:id=>artists.id, :name=>artists.name}, :albums=>nil}

Arguments:

  • dataset - Can be a symbol (specifying a table), another dataset, or an object that responds to .dataset and yields a symbol or a dataset

  • join_conditions - Any condition(s) allowed by join_table.

  • options - A hash of graph options. The following options are currently used:

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

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

    • :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 join that makes it important to use graph instead of join.

  • block - A block that is passed to join_table.



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# File 'lib/sequel_core/object_graph.rb', line 47

def graph(dataset, join_conditions = nil, options = {}, &block)
  # Allow the use of a model, dataset, or symbol as the first argument
  # Find the table name/dataset based on the argument
  dataset = dataset.dataset if dataset.respond_to?(:dataset)
  case dataset
  when Symbol
    table = dataset
    dataset = @db[dataset]
  when ::Sequel::Dataset
    table = dataset.first_source
  else
    raise Error, "The dataset argument should be a symbol, dataset, or model"
  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
  table_alias = options[:table_alias] || table
  raise_alias_error.call if @opts[:graph] && @opts[:graph][:table_aliases] && @opts[:graph][:table_aliases].include?(table_alias)

  # Join the table early in order to avoid cloning the dataset twice
  ds = join_table(options[:join_type] || :left_outer, table, join_conditions, table_alias, &block)
  opts = ds.opts

  # Whether to include the table in the result set
  add_table = options[:select] == false ? false : true
  # Whether to add the columns to the list of column aliases
  add_columns = !ds.opts.include?(:graph_aliases)

  # Setup the initial graph data structure if it doesn't exist
  unless graph = opts[:graph]
    master = ds.first_source
    raise_alias_error.call if master == table_alias
    # Master hash storing all .graph related information
    graph = opts[: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)
    # All columns in the master table are never
    # aliased, but are not included if set_graph_aliases
    # has been used.
    if add_columns
      select = opts[:select] = []
      columns.each do |column|
        column_aliases[column] = [master, column]
        select.push(column.qualify(master))
      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 && add_columns
    select = opts[:select]
    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, column.qualify(table_alias).as(column_alias)]
      else
        [column, column.qualify(table_alias)]
      end
      column_aliases[col_alias] = [table_alias, column]
      select.push(identifier)
    end
  end
  ds
end

#grep(cols, terms) ⇒ Object

Pattern match any of the columns to any of the terms. The terms can be strings (which use LIKE) or regular expressions (which are only supported in some databases). See Sequel::SQL::StringExpression.like. Note that the total number of pattern matches will be cols.length * terms.length, which could cause performance issues.



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# File 'lib/sequel_core/dataset/sql.rb', line 229

def grep(cols, terms)
  filter(SQL::BooleanExpression.new(:OR, *Array(cols).collect{|c| SQL::StringExpression.like(c, *terms)}))
end

#group(*columns) ⇒ Object Also known as: group_by

Returns a copy of the dataset with the results grouped by the value of the given columns



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# File 'lib/sequel_core/dataset/sql.rb', line 235

def group(*columns)
  clone(:group => columns)
end

#group_and_count(*columns) ⇒ Object

Returns a dataset grouped by the given column with count by group.



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# File 'lib/sequel_core/dataset/convenience.rb', line 69

def group_and_count(*columns)
  group(*columns).select(*(columns + [COUNT_OF_ALL_AS_COUNT])).order(:count)
end

#having(*cond, &block) ⇒ Object

Returns a copy of the dataset with the having conditions changed. Raises an error if the dataset has not been grouped. See also #filter.

Raises:



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# File 'lib/sequel_core/dataset/sql.rb', line 242

def having(*cond, &block)
  raise(Error::InvalidOperation, "Can only specify a HAVING clause on a grouped dataset") unless @opts[:group]
  clone(:having=>{}).filter(*cond, &block)
end

#insert(*values) ⇒ Object

Inserts values into the associated table. The returned value is generally the value of the primary key for the inserted row, but that is adapter dependent.



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# File 'lib/sequel_core/dataset.rb', line 218

def insert(*values)
  execute_dui(insert_sql(*values))
end

#insert_multiple(array, &block) ⇒ Object

Inserts multiple values. If a block is given it is invoked for each item in the given array before inserting it. See #multi_insert as a possible faster version that inserts multiple records in one SQL statement.



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# File 'lib/sequel_core/dataset/sql.rb', line 251

def insert_multiple(array, &block)
  if block
    array.each {|i| insert(block[i])}
  else
    array.each {|i| insert(i)}
  end
end

#insert_sql(*values) ⇒ Object

Formats an INSERT statement using the given values. If a hash is given, the resulting statement includes column names. If no values are given, the resulting statement includes a DEFAULT VALUES clause.

dataset.insert_sql() #=> 'INSERT INTO items DEFAULT VALUES'
dataset.insert_sql(1,2,3) #=> 'INSERT INTO items VALUES (1, 2, 3)'
dataset.insert_sql(:a => 1, :b => 2) #=>
  'INSERT INTO items (a, b) VALUES (1, 2)'



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# File 'lib/sequel_core/dataset/sql.rb', line 267

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

  from = source_list(@opts[:from])
  case values.size
  when 0
    values = {}
  when 1
    vals = values.at(0)
    if vals.is_one_of?(Hash, Dataset, Array)
      values = vals
    elsif vals.respond_to?(:values)
      values = vals.values
    end
  end

  case values
  when Array
    if values.empty?
      insert_default_values_sql
    else
      "INSERT INTO #{from} VALUES #{literal(values)}"
    end
  when Hash
    values = @opts[:defaults].merge(values) if @opts[:defaults]
    values = values.merge(@opts[:overrides]) if @opts[:overrides]
    values = transform_save(values) if @transform
    if values.empty?
      insert_default_values_sql
    else
      fl, vl = [], []
      values.each do |k, v|
        fl << literal(String === k ? k.to_sym : k)
        vl << literal(v)
      end
      "INSERT INTO #{from} (#{fl.join(COMMA_SEPARATOR)}) VALUES (#{vl.join(COMMA_SEPARATOR)})"
    end
  when Dataset
    "INSERT INTO #{from} #{literal(values)}"
  end
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_core/dataset.rb', line 224

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

#intersect(dataset, all = false) ⇒ Object

Adds an INTERSECT clause using a second dataset object. If all is true the clause used is INTERSECT ALL, which may return duplicate rows.

DB[:items].intersect(DB[:other_items]).sql
#=> "SELECT * FROM items INTERSECT SELECT * FROM other_items"



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# File 'lib/sequel_core/dataset/sql.rb', line 316

def intersect(dataset, all = false)
  clone(:intersect => dataset, :intersect_all => all)
end

#interval(column) ⇒ Object

Returns the interval between minimum and maximum values for the given column.



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# File 'lib/sequel_core/dataset/convenience.rb', line 75

def interval(column)
  get("(max(#{literal(column)}) - min(#{literal(column)}))".lit)
end

#invert ⇒ Object

Inverts the current filter

dataset.filter(:category => 'software').invert.sql #=>
  "SELECT * FROM items WHERE (category != 'software')"

Raises:



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# File 'lib/sequel_core/dataset/sql.rb', line 324

def invert
  having, where = @opts[:having], @opts[:where]
  raise(Error, "No current filter") unless having || where
  o = {}
  o[:having] = SQL::BooleanExpression.invert(having) if having
  o[:where] = SQL::BooleanExpression.invert(where) if where
  clone(o)
end

#irregular_function_sql(f) ⇒ Object

SQL fragment specifying an Irregular (cast/extract) SQL function call



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# File 'lib/sequel_core/dataset/sql.rb', line 334

def irregular_function_sql(f)
  "#{f.f}(#{literal(f.arg1)} #{f.joiner} #{literal(f.arg2)})"
end

#join_clause_sql(jc) ⇒ Object

SQL fragment specifying a JOIN clause without ON or USING.



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# File 'lib/sequel_core/dataset/sql.rb', line 339

def join_clause_sql(jc)
  table = jc.table
  table_alias = jc.table_alias
  table_alias = nil if table == table_alias
  tref = table_ref(table)
  " #{join_type_sql(jc.join_type)} #{table_alias ? as_sql(tref, table_alias) : tref}"
end

#join_on_clause_sql(jc) ⇒ Object

SQL fragment specifying a JOIN clause with ON.



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# File 'lib/sequel_core/dataset/sql.rb', line 348

def join_on_clause_sql(jc)
  "#{join_clause_sql(jc)} ON #{literal(filter_expr(jc.on))}"
end

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

Returns a joined dataset. Uses the following arguments:

  • type - The type of join to do (:inner, :left_outer, :right_outer, :full)

  • table - Depends on type:

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

    • Model (or anything responding to :table_name) - table.table_name

    • String, Symbol: table

  • expr - specifies conditions, depends on type:

    • Hash, Array with all two 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. 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 a ON clause based on the block, see below.

    • Everything else - pretty much the same as a using the argument in a call to filter, so strings are considered literal, symbols specify boolean columns, and blockless filter expressions can be used. Uses a JOIN with an ON clause.

  • table_alias - the name of the table’s alias when joining, necessary for joining to the same table more than once. No alias is used by default.

  • 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.



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# File 'lib/sequel_core/dataset/sql.rb', line 383

def join_table(type, table, expr=nil, table_alias=nil, &block)
  if Dataset === table
    if table_alias.nil?
      table_alias_num = (@opts[:num_dataset_sources] || 0) + 1
      table_alias = "t#{table_alias_num}"
    end
    table_name = table_alias
  else
    table = table.table_name if table.respond_to?(:table_name)
    table_name = table_alias || table
  end

  join = if expr.nil? and !block_given?
    SQL::JoinClause.new(type, table, table_alias)
  elsif Array === expr and !expr.empty? and expr.all?{|x| Symbol === x}
    raise(Sequel::Error, "can't use a block if providing an array of symbols as expr") if block_given?
    SQL::JoinUsingClause.new(expr, type, table, table_alias)
  else
    last_alias = @opts[:last_joined_table] || (first_source.is_a?(Dataset) ? 't1' : first_source)
    if Hash === expr or (Array === expr and expr.all_two_pairs?)
      expr = expr.collect do |k, v|
        k = qualified_column_name(k, table_name) if k.is_a?(Symbol)
        v = qualified_column_name(v, last_alias) if v.is_a?(Symbol)
        [k,v]
      end
    end
    if block_given?
      expr2 = yield(table_name, last_alias, @opts[:join] || [])
      expr = expr ? SQL::BooleanExpression.new(:AND, expr, expr2) : expr2
    end
    SQL::JoinOnClause.new(expr, type, table, table_alias)
  end

  opts = {:join => (@opts[:join] || []) + [join], :last_joined_table => table_name}
  opts[:num_dataset_sources] = table_alias_num if table_alias_num
  clone(opts)
end

#join_using_clause_sql(jc) ⇒ Object

SQL fragment specifying a JOIN clause with USING.



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# File 'lib/sequel_core/dataset/sql.rb', line 353

def join_using_clause_sql(jc)
  "#{join_clause_sql(jc)} USING (#{column_list(jc.using)})"
end

#last(*args, &block) ⇒ Object

Reverses the order and then runs first. 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.

Raises:



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# File 'lib/sequel_core/dataset/convenience.rb', line 83

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

#limit(l, o = 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.

Raises:



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# File 'lib/sequel_core/dataset/sql.rb', line 424

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

  if Range === l
    o = l.first
    l = l.interval + 1
  end
  l = l.to_i
  raise(Error, 'Limits must be greater than or equal to 1') unless l >= 1
  opts = {:limit => l}
  if o
    o = o.to_i
    raise(Error, 'Offsets must be greater than or equal to 0') unless o >= 0
    opts[:offset] = o
  end
  clone(opts)
end

#literal(v) ⇒ Object

Returns a literal representation of a value to be used as part of an SQL expression. 

dataset.literal("abc'def\\") #=> "'abc''def\\\\'"
dataset.literal(:items__id) #=> "items.id"
dataset.literal([1, 2, 3]) => "(1, 2, 3)"
dataset.literal(DB[:items]) => "(SELECT * FROM items)"
dataset.literal(:x + 1 > :y) => "((x + 1) > y)"

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



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# File 'lib/sequel_core/dataset/sql.rb', line 452

def literal(v)
  case v
  when LiteralString
    v
  when String
    "'#{v.gsub(/\\/, "\\\\\\\\").gsub(/'/, "''")}'"
  when Integer, Float
    v.to_s
  when BigDecimal
    v.to_s("F")
  when NilClass
    NULL
  when TrueClass
    BOOL_TRUE
  when FalseClass
    BOOL_FALSE
  when Symbol
    symbol_to_column_ref(v)
  when ::Sequel::SQL::Expression
    v.to_s(self)
  when Array
    v.all_two_pairs? ? literal(v.sql_expr) : (v.empty? ? '(NULL)' : "(#{expression_list(v)})")
  when Hash
    literal(v.sql_expr)
  when Time, DateTime
    v.strftime(TIMESTAMP_FORMAT)
  when Date
    v.strftime(DATE_FORMAT)
  when Dataset
    "(#{v.sql})"
  else
    raise Error, "can't express #{v.inspect} as a SQL literal"
  end
end

#map(column_name = nil, &block) ⇒ Object

Maps column values for each record in the dataset (if a column name is given), or performs the stock mapping functionality of Enumerable.



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# File 'lib/sequel_core/dataset/convenience.rb', line 90

def map(column_name = nil, &block)
  if column_name
    super() {|r| r[column_name]}
  else
    super(&block)
  end
end

#max(column) ⇒ Object

Returns the maximum value for the given column.



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# File 'lib/sequel_core/dataset/convenience.rb', line 99

def max(column)
  get(:max[column])
end

#min(column) ⇒ Object

Returns the minimum value for the given column.



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# File 'lib/sequel_core/dataset/convenience.rb', line 104

def min(column)
  get(:min[column])
end

#model_classes ⇒ Object

Returns the the model classes associated with the dataset as a hash. If the dataset is associated with a single model class, a key of nil is used. For datasets with polymorphic models, the keys are values of the polymorphic column and the values are the corresponding model classes to which they map.



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# File 'lib/sequel_core/dataset.rb', line 233

def model_classes
  @opts[:models]
end

#multi_insert(*args) ⇒ Object Also known as: import

Inserts multiple records into the associated table. This method can be to efficiently insert a large amounts of records into a table. Inserts are automatically wrapped in a transaction.

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

dataset.multi_insert([:x, :y], [[1, 2], [3, 4]])

This method can also be called with an array of hashes:

dataset.multi_insert({:x => 1}, {:x => 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.

The method also accepts a :slice or :commit_every option that specifies the number of records to insert per transaction. This is useful especially when inserting a large number of records, e.g.:

# this will commit every 50 records
dataset.multi_insert(lots_of_records, :slice => 50)



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# File 'lib/sequel_core/dataset/convenience.rb', line 130

def multi_insert(*args)
  if args.empty?
    return
  elsif args[0].is_a?(Array) && args[1].is_a?(Array)
    columns, values, opts = *args
  elsif args[0].is_a?(Array) && args[1].is_a?(Dataset)
    table = @opts[:from].first
    columns, dataset = *args
    sql = "INSERT INTO #{quote_identifier(table)} (#{identifier_list(columns)}) VALUES #{literal(dataset)}"
    return @db.transaction{execute_dui(sql)}
  else
    # we assume that an array of hashes is given
    hashes, opts = *args
    return if hashes.empty?
    columns = hashes.first.keys
    # convert the hashes into arrays
    values = hashes.map {|h| columns.map {|c| h[c]}}
  end
  # make sure there's work to do
  return if columns.empty? || values.empty?
  
  slice_size = opts && (opts[:commit_every] || opts[:slice])
  
  if slice_size
    values.each_slice(slice_size) do |slice|
      statements = multi_insert_sql(columns, slice)
      @db.transaction{statements.each{|st| execute_dui(st)}}
    end
  else
    statements = multi_insert_sql(columns, values)
    @db.transaction{statements.each{|st| execute_dui(st)}}
  end
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.

This method should be overridden by descendants if the support inserting multiple records in a single SQL statement.



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# File 'lib/sequel_core/dataset/sql.rb', line 493

def multi_insert_sql(columns, values)
  table = quote_identifier(@opts[:from].first)
  columns = identifier_list(columns)
  values.map do |r|
    "INSERT INTO #{table} (#{columns}) VALUES #{literal(r)}"
  end
end

#naked ⇒ Object

Returns a naked dataset clone - i.e. a dataset that returns records as hashes rather than model objects.



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# File 'lib/sequel_core/dataset.rb', line 239

def naked
  clone.set_model(nil)
end

#or(*cond, &block) ⇒ Object

Adds an alternate filter to an existing filter using OR. If no filter exists an error is raised.



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# File 'lib/sequel_core/dataset/sql.rb', line 503

def or(*cond, &block)
  clause = (@opts[:having] ? :having : :where)
  cond = cond.first if cond.size == 1
  if @opts[clause]
    clone(clause => SQL::BooleanExpression.new(:OR, @opts[clause], filter_expr(cond, &block)))
  else
    raise Error::NoExistingFilter, "No existing filter found."
  end
end

#order(*order) ⇒ Object Also known as: order_by

Returns a copy of the dataset with the order changed. If a nil is given the returned dataset has no order. This can accept multiple arguments of varying kinds, and even SQL functions.

ds.order(:name).sql #=> 'SELECT * FROM items ORDER BY name'
ds.order(:a, :b).sql #=> 'SELECT * FROM items ORDER BY a, b'
ds.order('a + b'.lit).sql #=> 'SELECT * FROM items ORDER BY a + b'
ds.order(:a + :b).sql #=> 'SELECT * FROM items ORDER BY (a + b)'
ds.order(:name.desc).sql #=> 'SELECT * FROM items ORDER BY name DESC'
ds.order(:name.asc).sql #=> 'SELECT * FROM items ORDER BY name ASC'
ds.order(:arr|1).sql #=> 'SELECT * FROM items ORDER BY arr[1]'
ds.order(nil).sql #=> 'SELECT * FROM items'



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# File 'lib/sequel_core/dataset/sql.rb', line 525

def order(*order)
  clone(:order => (order.compact.empty?) ? nil : order)
end

#order_more(*order) ⇒ Object

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



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# File 'lib/sequel_core/dataset/sql.rb', line 532

def order_more(*order)
  order(*((@opts[:order] || []) + order))
end

#ordered_expression_sql(oe) ⇒ Object

SQL fragment for the ordered expression, used in the ORDER BY clause.



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# File 'lib/sequel_core/dataset/sql.rb', line 538

def ordered_expression_sql(oe)
  "#{literal(oe.expression)} #{oe.descending ? 'DESC' : 'ASC'}"
end

#paginate(page_no, page_size, record_count = nil) ⇒ Object

Returns a paginated dataset. The returned dataset is limited to the page size at the correct offset, and extended with the Pagination module. If a record count is not provided, does a count of total number of records for this dataset.

Raises:



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# File 'lib/sequel_core/dataset/pagination.rb', line 7

def paginate(page_no, page_size, record_count=nil)
  raise(Error, "You cannot paginate a dataset that already has a limit") if @opts[:limit]
  paginated = limit(page_size, (page_no - 1) * page_size)
  paginated.extend(Pagination)
  paginated.set_pagination_info(page_no, page_size, record_count || count)
end

#polymorphic_key ⇒ Object

Returns the column name for the polymorphic key.



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# File 'lib/sequel_core/dataset.rb', line 244

def polymorphic_key
  @opts[:polymorphic_key]
end

#prepare(type, name, values = nil) ⇒ Object

Prepare an SQL statement for later execution. This returns a clone of the dataset extended with PreparedStatementMethods, on which you can call call with the hash of bind variables to do substitution. The prepared statement is also stored in the associated database. The following usage is identical:

ps = prepare(:select, :select_by_name)
ps.call(:name=>'Blah')
db.call(:select_by_name, :name=>'Blah')



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# File 'lib/sequel_core/dataset/prepared_statements.rb', line 196

def prepare(type, name, values=nil)
  db.prepared_statements[name] = to_prepared_statement(type, values)
end

#print(*cols) ⇒ Object

Pretty prints the records in the dataset as plain-text table.



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# File 'lib/sequel_core/dataset/convenience.rb', line 166

def print(*cols)
  Sequel::PrettyTable.print(naked.all, cols.empty? ? columns : cols)
end

#qualified_identifier_sql(qcr) ⇒ Object

SQL fragment for the qualifed identifier, specifying a table and a column (or schema and table).



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# File 'lib/sequel_core/dataset/sql.rb', line 544

def qualified_identifier_sql(qcr)
  [qcr.table, qcr.column].map{|x| x.is_one_of?(SQL::QualifiedIdentifier, SQL::Identifier) ? literal(x) : quote_identifier(x)}.join('.')
end

#query(&block) ⇒ Object

Translates a query block into a dataset. Query blocks can be useful when expressing complex SELECT statements, e.g.:

dataset = DB[:items].query do
  select :x, :y, :z
  filter((:x > 1) & (:y > 2))
  order :z.desc
end

Which is the same as:

dataset = DB[:items].select(:x, :y, :z).filter((:x > 1) & (:y > 2)).order(:z.desc)

Note that inside a call to query, you cannot call each, insert, update, or delete (or any method that calls those), or Sequel will raise an error.



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# File 'lib/sequel_core/dataset/query.rb', line 19

def query(&block)
  copy = clone({})
  copy.extend(QueryBlockCopy)
  copy.instance_eval(&block)
  clone(copy.opts)
end

#quote_identifier(name) ⇒ Object Also known as: quote_column_ref

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_core/dataset/sql.rb', line 551

def quote_identifier(name)
  quote_identifiers? ? quoted_identifier(name) : name.to_s
end

#quote_identifiers? ⇒ Boolean

Whether this dataset quotes identifiers.

Returns:

  • (Boolean) 


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# File 'lib/sequel_core/dataset.rb', line 249

def quote_identifiers?
  @quote_identifiers
end

#quoted_identifier(name) ⇒ Object

This method quotes the given name with the SQL standard double quote. It uppercases the name given to conform with the SQL standard. This should be overridden by subclasses to provide quoting not matching the SQL standard, such as backtick (used by MySQL and SQLite), or where lowercase is the default for unquoted identifiers (PostgreSQL).

If you are using a database such as Oracle that defaults to uppercase but you are using lower case identifiers, you should override this method to not upcase the name for those identifiers.



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# File 'lib/sequel_core/dataset/sql.rb', line 565

def quoted_identifier(name)
  "\"#{name.to_s.upcase}\""
end

#range(column) ⇒ Object

Returns a Range object made from the minimum and maximum values for the given column.



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# File 'lib/sequel_core/dataset/convenience.rb', line 172

def range(column)
  if r = select(:min[column].as(:v1), :max[column].as(:v2)).first
    (r[:v1]..r[:v2])
  end
end

#reverse_order(*order) ⇒ Object Also known as: reverse

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



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# File 'lib/sequel_core/dataset/sql.rb', line 571

def reverse_order(*order)
  order(*invert_order(order.empty? ? @opts[:order] : order))
end

#select(*columns) ⇒ Object

Returns a copy of the dataset with the columns selected changed to the given columns.



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# File 'lib/sequel_core/dataset/sql.rb', line 578

def select(*columns)
  clone(:select => columns)
end

#select_all ⇒ Object

Returns a copy of the dataset selecting the wildcard.



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

def select_all
  clone(:select => nil)
end

#select_more(*columns) ⇒ Object

Returns a copy of the dataset with the given columns added to the existing selected columns.



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# File 'lib/sequel_core/dataset/sql.rb', line 589

def select_more(*columns)
  select(*((@opts[:select] || []) + columns))
end

#select_sql(opts = nil) ⇒ Object Also known as: sql

Formats a SELECT statement using the given options and the dataset options.



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# File 'lib/sequel_core/dataset/sql.rb', line 595

def select_sql(opts = nil)
  opts = opts ? @opts.merge(opts) : @opts
  
  if sql = opts[:sql]
    return sql
  end

  columns = opts[:select]
  select_columns = columns ? column_list(columns) : WILDCARD

  if distinct = opts[:distinct]
    distinct_clause = distinct.empty? ? "DISTINCT" : "DISTINCT ON (#{expression_list(distinct)})"
    sql = "SELECT #{distinct_clause} #{select_columns}"
  else
    sql = "SELECT #{select_columns}"
  end
  
  if opts[:from]
    sql << " FROM #{source_list(opts[:from])}"
  end
  
  if join = opts[:join]
    join.each{|j| sql << literal(j)}
  end

  if where = opts[:where]
    sql << " WHERE #{literal(where)}"
  end

  if group = opts[:group]
    sql << " GROUP BY #{expression_list(group)}"
  end

  if having = opts[:having]
    sql << " HAVING #{literal(having)}"
  end

  if order = opts[:order]
    sql << " ORDER BY #{expression_list(order)}"
  end

  if limit = opts[:limit]
    sql << " LIMIT #{limit}"
    if offset = opts[:offset]
      sql << " OFFSET #{offset}"
    end
  end

  if union = opts[:union]
    sql << (opts[:union_all] ? \
      " UNION ALL #{union.sql}" : " UNION #{union.sql}")
  elsif intersect = opts[:intersect]
    sql << (opts[:intersect_all] ? \
      " INTERSECT ALL #{intersect.sql}" : " INTERSECT #{intersect.sql}")
  elsif except = opts[:except]
    sql << (opts[:except_all] ? \
      " EXCEPT ALL #{except.sql}" : " EXCEPT #{except.sql}")
  end

  sql
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 SELECT uses :read_only database and all other queries use the :default database.



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# File 'lib/sequel_core/dataset.rb', line 256

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

#set(*args) ⇒ Object

Alias for set, but not aliased directly so subclasses don’t have to override both methods.



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# File 'lib/sequel_core/dataset.rb', line 262

def set(*args)
  update(*args)
end

#set_defaults(hash) ⇒ Object

Set the default values for insert and update statements. The values passed to insert or update are merged into this hash.



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# File 'lib/sequel_core/dataset.rb', line 268

def set_defaults(hash)
  clone(:defaults=>(@opts[:defaults]||{}).merge(hash))
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. Example:

DB[:artists].graph(:albums, :artist_id=>:id).set_graph_aliases(:artist_name=>[:artists, :name], :album_name=>[:albums, :name]).first
=> {:artists=>{:name=>artists.name}, :albums=>{:name=>albums.name}}

Arguments:

  • graph_aliases - Should be a hash with keys being symbols of column aliases, and values being arrays with two symbol elements. The first element of the array should be the table alias, and the second should be the actual column name.



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# File 'lib/sequel_core/object_graph.rb', line 157

def set_graph_aliases(graph_aliases)
  cols = graph_aliases.collect do |col_alias, tc| 
    identifier = tc[1].qualify(tc[0])
    identifier = identifier.as(col_alias) unless tc[1] == col_alias
    identifier
  end
  ds = select(*cols)
  ds.opts[:graph_aliases] = graph_aliases
  ds
end

#set_model(key, *args) ⇒ Object

Associates or disassociates the dataset with a model(s). If nil is specified, the dataset is turned into a naked dataset and returns records as hashes. If a model class specified, the dataset is modified to return records as instances of the model class, e.g:

class MyModel
  def initialize(values)
    @values = values
    ...
  end
end

dataset.set_model(MyModel)

You can also provide additional arguments to be passed to the model’s initialize method:

class MyModel
  def initialize(values, options)
    @values = values
    ...
  end
end

dataset.set_model(MyModel, :allow_delete => false)

The dataset can be made polymorphic by specifying a column name as the polymorphic key and a hash mapping column values to model classes.

dataset.set_model(:kind, {1 => Person, 2 => Business})

You can also set a default model class to fall back on by specifying a class corresponding to nil:

dataset.set_model(:kind, {nil => DefaultClass, 1 => Person, 2 => Business})

To make sure that there is always a default model class, the hash provided should have a default value. To make the dataset map string values to model classes, and keep a good default, try:

dataset.set_model(:kind, Hash.new{|h,k| h[k] = (k.constantize rescue DefaultClass)})



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# File 'lib/sequel_core/dataset.rb', line 313

def set_model(key, *args)
  # This code is more verbose then necessary for performance reasons
  case key
  when nil # set_model(nil) => no argument provided, so the dataset is denuded
    @opts.merge!(:naked => true, :models => nil, :polymorphic_key => nil)
    self.row_proc = nil
  when Class
    # isomorphic model
    @opts.merge!(:naked => nil, :models => {nil => key}, :polymorphic_key => nil)
    if key.respond_to?(:load)
      # the class has a values setter method, so we use it
      self.row_proc = proc{|h| key.load(h, *args)}
    else
      # otherwise we just pass the hash to the constructor
      self.row_proc = proc{|h| key.new(h, *args)}
    end
  when Symbol
    # polymorphic model
    hash = args.shift || raise(ArgumentError, "No class hash supplied for polymorphic model")
    @opts.merge!(:naked => true, :models => hash, :polymorphic_key => key)
    if (hash.empty? ? (hash[nil] rescue nil) : hash.values.first).respond_to?(:load)
      # the class has a values setter method, so we use it
      self.row_proc = proc do |h|
        c = hash[h[key]] || hash[nil] || \
          raise(Error, "No matching model class for record (#{polymorphic_key} => #{h[polymorphic_key].inspect})")
        c.load(h, *args)
      end
    else
      # otherwise we just pass the hash to the constructor
      self.row_proc = proc do |h|
        c = hash[h[key]] || hash[nil] || \
          raise(Error, "No matching model class for record (#{polymorphic_key} => #{h[polymorphic_key].inspect})")
        c.new(h, *args)
      end
    end
  else
    raise ArgumentError, "Invalid model specified"
  end
  self
end

#set_overrides(hash) ⇒ Object

Set values that override hash arguments given to insert and update statements. This hash is merged into the hash provided to insert or update.



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# File 'lib/sequel_core/dataset.rb', line 356

def set_overrides(hash)
  clone(:overrides=>hash.merge(@opts[:overrides]||{}))
end

#single_record(opts = nil) ⇒ Object

Returns the first record in the dataset.



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# File 'lib/sequel_core/dataset/convenience.rb', line 179

def single_record(opts = nil)
  each((opts||{}).merge(:limit=>1)){|r| return r}
  nil
end

#single_value(opts = nil) ⇒ Object

Returns the first value of the first record in the dataset. Returns nil if dataset is empty.



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# File 'lib/sequel_core/dataset/convenience.rb', line 186

def single_value(opts = nil)
  if r = single_record((opts||{}).merge(:graph=>false, :naked=>true))
    r.values.first
  end
end

#subscript_sql(s) ⇒ Object

SQL fragment for specifying subscripts (SQL arrays)



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# File 'lib/sequel_core/dataset/sql.rb', line 659

def subscript_sql(s)
  "#{s.f}[#{s.sub.join(COMMA_SEPARATOR)}]"
end

#sum(column) ⇒ Object

Returns the sum for the given column.



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# File 'lib/sequel_core/dataset/convenience.rb', line 193

def sum(column)
  get(:sum[column])
end

#symbol_to_column_ref(sym) ⇒ Object

Converts a symbol into a column name. This method supports underscore notation in order to express qualified (two underscores) and aliased (three underscores) columns:

ds = DB[:items]
:abc.to_column_ref(ds) #=> "abc"
:abc___a.to_column_ref(ds) #=> "abc AS a"
:items__abc.to_column_ref(ds) #=> "items.abc"
:items__abc___a.to_column_ref(ds) #=> "items.abc AS a"



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# File 'lib/sequel_core/dataset/sql.rb', line 673

def symbol_to_column_ref(sym)
  c_table, column, c_alias = split_symbol(sym)
  qc = "#{"#{quote_identifier(c_table)}." if c_table}#{quote_identifier(column)}"
  c_alias ? as_sql(qc, c_alias) : qc
end

#table_exists? ⇒ Boolean

Returns true if the table exists. Will raise an error if the dataset has fixed SQL or selects from another dataset or more than one table.

Returns:

  • (Boolean) 


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# File 'lib/sequel_core/dataset/convenience.rb', line 200

def table_exists?
  if @opts[:sql]
    raise Sequel::Error, "this dataset has fixed SQL"
  end
  
  if @opts[:from].size != 1
    raise Sequel::Error, "this dataset selects from multiple sources"
  end
  
  t = @opts[:from].first
  if t.is_a?(Dataset)
    raise Sequel::Error, "this dataset selects from a sub query"
  end
  
  @db.table_exists?(t.to_sym)
end

#to_csv(include_column_titles = true) ⇒ Object

Returns a string in CSV format containing the dataset records. By default the CSV representation includes the column titles in the first line. You can turn that off by passing false as the include_column_titles argument.

This does not use a CSV library or handle quoting of values in any way. If any values in any of the rows could include commas or line endings, you probably shouldn’t use this.



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# File 'lib/sequel_core/dataset/convenience.rb', line 225

def to_csv(include_column_titles = true)
  n = naked
  cols = n.columns
  csv = ''
  csv << "#{cols.join(COMMA_SEPARATOR)}\r\n" if include_column_titles
  n.each{|r| csv << "#{cols.collect{|c| r[c]}.join(COMMA_SEPARATOR)}\r\n"}
  csv
end

#to_hash(key_column, value_column = nil) ⇒ 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.



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# File 'lib/sequel_core/dataset/convenience.rb', line 238

def to_hash(key_column, value_column = nil)
  inject({}) do |m, r|
    m[r[key_column]] = value_column ? r[value_column] : r
    m
  end
end

#transform(t) ⇒ Object

Sets a value transform which is used to convert values loaded and saved to/from the database. The transform should be supplied as a hash. Each value in the hash should be an array containing two proc objects - one for transforming loaded values, and one for transforming saved values. The following example demonstrates how to store Ruby objects in a dataset using Marshal serialization:

dataset.transform(:obj => [
  proc {|v| Marshal.load(v)},
  proc {|v| Marshal.dump(v)}
])

dataset.insert_sql(:obj => 1234) #=>
"INSERT INTO items (obj) VALUES ('\004\bi\002\322\004')"

Another form of using transform is by specifying stock transforms:

dataset.transform(:obj => :marshal)

The currently supported stock transforms are :marshal and :yaml.



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# File 'lib/sequel_core/dataset.rb', line 380

def transform(t)
  @transform = t
  t.each do |k, v|
    case v
    when Array
      if (v.size != 2) || !v.first.is_a?(Proc) && !v.last.is_a?(Proc)
        raise Error::InvalidTransform, "Invalid transform specified"
      end
    else
      unless v = STOCK_TRANSFORMS[v]
        raise Error::InvalidTransform, "Invalid transform specified"
      else
        t[k] = v
      end
    end
  end
  self
end

#transform_load(r) ⇒ Object

Applies the value transform for data loaded from the database.



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# File 'lib/sequel_core/dataset.rb', line 400

def transform_load(r)
  r.inject({}) do |m, kv|
    k, v = *kv
    m[k] = (tt = @transform[k]) ? tt[0][v] : v
    m
  end
end

#transform_save(r) ⇒ Object

Applies the value transform for data saved to the database.



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# File 'lib/sequel_core/dataset.rb', line 409

def transform_save(r)
  r.inject({}) do |m, kv|
    k, v = *kv
    m[k] = (tt = @transform[k]) ? tt[1][v] : v
    m
  end
end

#unfiltered ⇒ Object

Returns a copy of the dataset with no filters (HAVING or WHERE clause) applied.



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# File 'lib/sequel_core/dataset/sql.rb', line 680

def unfiltered
  clone(:where => nil, :having => nil)
end

#union(dataset, all = false) ⇒ Object

Adds a UNION clause using a second dataset object. If all is true the clause used is UNION ALL, which may return duplicate rows.

DB[:items].union(DB[:other_items]).sql
#=> "SELECT * FROM items UNION SELECT * FROM other_items"



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# File 'lib/sequel_core/dataset/sql.rb', line 689

def union(dataset, all = false)
  clone(:union => dataset, :union_all => all)
end

#uniq(*args) ⇒ Object Also known as: distinct

Returns a copy of the dataset with the distinct option.



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# File 'lib/sequel_core/dataset/sql.rb', line 694

def uniq(*args)
  clone(:distinct => args)
end

#unordered ⇒ Object

Returns a copy of the dataset with no order.



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# File 'lib/sequel_core/dataset/sql.rb', line 700

def unordered
  order(nil)
end

#update(*args) ⇒ Object

Updates values for the dataset. The returned value is generally the number of rows updated, but that is adapter dependent.



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# File 'lib/sequel_core/dataset.rb', line 419

def update(*args)
  execute_dui(update_sql(*args))
end

#update_sql(values = {}, opts = nil) ⇒ Object

Formats an UPDATE statement using the given values.

dataset.update_sql(:price => 100, :category => 'software') #=>
  "UPDATE items SET price = 100, category = 'software'"

Accepts a block, but such usage is discouraged.

Raises an error if the dataset is grouped or includes more than one table.



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# File 'lib/sequel_core/dataset/sql.rb', line 713

def update_sql(values = {}, opts = nil)
  opts = opts ? @opts.merge(opts) : @opts

  if sql = opts[:sql]
    return sql
  end

  if opts[:group]
    raise Error::InvalidOperation, "A grouped dataset cannot be updated"
  elsif (opts[:from].size > 1) or opts[:join]
    raise Error::InvalidOperation, "A joined dataset cannot be updated"
  end
  
  sql = "UPDATE #{source_list(@opts[:from])} SET "
  set = if values.is_a?(Hash)
    values = opts[:defaults].merge(values) if opts[:defaults]
    values = values.merge(opts[:overrides]) if opts[:overrides]
    # get values from hash
    values = transform_save(values) if @transform
    values.map do |k, v|
      "#{k.is_one_of?(String, Symbol) ? quote_identifier(k) : literal(k)} = #{literal(v)}"
    end.join(COMMA_SEPARATOR)
  else
    # copy values verbatim
    values
  end
  sql << set
  if where = opts[:where]
    sql << " WHERE #{literal(where)}"
  end

  sql
end