Module: Sequel::SQLite::DatasetMethods

Included in:
Amalgalite::Dataset, DataObjects::SQLite::Dataset, JDBC::SQLite::Dataset, Dataset, Sequel::Swift::SQLite::Dataset
Defined in:
lib/sequel/adapters/shared/sqlite.rb

Overview

Instance methods for datasets that connect to an SQLite database

Constant Summary collapse

SELECT_CLAUSE_METHODS = 
Dataset.clause_methods(:select, %w'distinct columns from join where group having compounds order limit')
COMMA_SEPARATOR = 
', '.freeze
CONSTANT_MAP = 
{:CURRENT_DATE=>"date(CURRENT_TIMESTAMP, 'localtime')".freeze, :CURRENT_TIMESTAMP=>"datetime(CURRENT_TIMESTAMP, 'localtime')".freeze, :CURRENT_TIME=>"time(CURRENT_TIMESTAMP, 'localtime')".freeze}
EXTRACT_MAP = 
{:year=>"'%Y'", :month=>"'%m'", :day=>"'%d'", :hour=>"'%H'", :minute=>"'%M'", :second=>"'%f'"}

Instance Method Summary collapse

Instance Method Details

#complex_expression_sql(op, args) ⇒ Object

SQLite does not support pattern matching via regular expressions. SQLite is case insensitive (depending on pragma), so use LIKE for ILIKE.



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# File 'lib/sequel/adapters/shared/sqlite.rb', line 407

def complex_expression_sql(op, args)
  case op
  when :~, :'!~', :'~*', :'!~*'
    raise Error, "SQLite does not support pattern matching via regular expressions"
  when :ILIKE
    super(:LIKE, args.map{|a| SQL::Function.new(:upper, a)})
  when :"NOT LIKE", :"NOT ILIKE"
    "NOT #{complex_expression_sql((op == :"NOT ILIKE" ? :ILIKE : :LIKE), args)}"
  when :^
    complex_expression_arg_pairs(args) do |a, b|
      a = literal(a)
      b = literal(b)
      "((~(#{a} & #{b})) & (#{a} | #{b}))"
    end
  when :extract
    part = args.at(0)
    raise(Sequel::Error, "unsupported extract argument: #{part.inspect}") unless format = EXTRACT_MAP[part]
    expr = args.at(1)
    "CAST(strftime(#{format}, #{literal(expr)}) AS #{part == :second ? 'NUMERIC' : 'INTEGER'})"
  else
    super(op, args)
  end
end

#constant_sql(constant) ⇒ Object

MSSQL doesn’t support the SQL standard CURRENT_DATE or CURRENT_TIME



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# File 'lib/sequel/adapters/shared/sqlite.rb', line 432

def constant_sql(constant)
  CONSTANT_MAP[constant] || super
end

#delete ⇒ Object

SQLite performs a TRUNCATE style DELETE if no filter is specified. Since we want to always return the count of records, add a condition that is always true and then delete.



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# File 'lib/sequel/adapters/shared/sqlite.rb', line 439

def delete
  @opts[:where] ? super : filter(1=>1).delete
end

#explain ⇒ Object

Return an array of strings specifying a query explanation for a SELECT of the current dataset.



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# File 'lib/sequel/adapters/shared/sqlite.rb', line 445

def explain
  db.send(:metadata_dataset).clone(:sql=>"EXPLAIN #{select_sql}").
    map{|x| "#{x[:addr]}|#{x[:opcode]}|#{(1..5).map{|i| x[:"p#{i}"]}.join('|')}|#{x[:comment]}"}
end

#having(*cond) ⇒ Object

HAVING requires GROUP BY on SQLite

Raises:



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# File 'lib/sequel/adapters/shared/sqlite.rb', line 451

def having(*cond)
  raise(InvalidOperation, "Can only specify a HAVING clause on a grouped dataset") unless @opts[:group]
  super
end

#quoted_identifier(c) ⇒ Object

SQLite uses the nonstandard ‘ (backtick) for quoting identifiers.



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# File 'lib/sequel/adapters/shared/sqlite.rb', line 457

def quoted_identifier(c)
  "`#{c}`"
end

#select(*cols) ⇒ Object

When a qualified column is selected on SQLite and the qualifier is a subselect, the column name used is the full qualified name (including the qualifier) instead of just the column name. To get correct column names, you must use an alias.



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# File 'lib/sequel/adapters/shared/sqlite.rb', line 465

def select(*cols)
  if ((f = @opts[:from]) && f.any?{|t| t.is_a?(Dataset) || (t.is_a?(SQL::AliasedExpression) && t.expression.is_a?(Dataset))}) || ((j = @opts[:join]) && j.any?{|t| t.table.is_a?(Dataset)})
    super(*cols.map{|c| alias_qualified_column(c)})
  else
    super
  end
end

#supports_intersect_except_all? ⇒ Boolean

SQLite does not support INTERSECT ALL or EXCEPT ALL

Returns:

  • (Boolean) 


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# File 'lib/sequel/adapters/shared/sqlite.rb', line 474

def supports_intersect_except_all?
  false
end

#supports_is_true? ⇒ Boolean

SQLite does not support IS TRUE

Returns:

  • (Boolean) 


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# File 'lib/sequel/adapters/shared/sqlite.rb', line 479

def supports_is_true?
  false
end

#supports_multiple_column_in? ⇒ Boolean

SQLite does not support multiple columns for the IN/NOT IN operators

Returns:

  • (Boolean) 


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# File 'lib/sequel/adapters/shared/sqlite.rb', line 484

def supports_multiple_column_in?
  false
end

#supports_timestamp_timezones? ⇒ Boolean

SQLite supports timezones in literal timestamps, since it stores them as text. But using timezones in timestamps breaks SQLite datetime functions, so we allow the user to override the default per database.

Returns:

  • (Boolean) 


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# File 'lib/sequel/adapters/shared/sqlite.rb', line 491

def supports_timestamp_timezones?
  db.use_timestamp_timezones?
end

#supports_where_true? ⇒ Boolean

SQLite cannot use WHERE ‘t’.

Returns:

  • (Boolean) 


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# File 'lib/sequel/adapters/shared/sqlite.rb', line 496

def supports_where_true?
  false
end