Module Sequel::SQLite::DatasetMethods
In: lib/sequel/adapters/shared/sqlite.rb

Instance methods for datasets that connect to an SQLite database

Methods

Included Modules

Dataset::Replace

Constants

SELECT_CLAUSE_METHODS = Dataset.clause_methods(:select, %w'select distinct columns from join where group having compounds order limit')
CONSTANT_MAP = {:CURRENT_DATE=>"date(CURRENT_TIMESTAMP, 'localtime')".freeze, :CURRENT_TIMESTAMP=>"datetime(CURRENT_TIMESTAMP, 'localtime')".freeze, :CURRENT_TIME=>"time(CURRENT_TIMESTAMP, 'localtime')".freeze}
EMULATED_FUNCTION_MAP = {:char_length=>'length'.freeze}
EXTRACT_MAP = {:year=>"'%Y'", :month=>"'%m'", :day=>"'%d'", :hour=>"'%H'", :minute=>"'%M'", :second=>"'%f'"}
NOT_SPACE = Dataset::NOT_SPACE
COMMA = Dataset::COMMA
PAREN_CLOSE = Dataset::PAREN_CLOSE
AS = Dataset::AS
APOS = Dataset::APOS
EXTRACT_OPEN = "CAST(strftime(".freeze
EXTRACT_CLOSE = ') AS '.freeze
NUMERIC = 'NUMERIC'.freeze
INTEGER = 'INTEGER'.freeze
BACKTICK = '`'.freeze
BACKTICK_RE = /`/.freeze
DOUBLE_BACKTICK = '``'.freeze
BLOB_START = "X'".freeze
HSTAR = "H*".freeze
DATE_OPEN = "date(".freeze
DATETIME_OPEN = "datetime(".freeze

Public Instance methods

[Source]

     # File lib/sequel/adapters/shared/sqlite.rb, line 501
501:       def cast_sql_append(sql, expr, type)
502:         if type == Time or type == DateTime
503:           sql << DATETIME_OPEN
504:           literal_append(sql, expr)
505:           sql << PAREN_CLOSE
506:         elsif type == Date
507:           sql << DATE_OPEN
508:           literal_append(sql, expr)
509:           sql << PAREN_CLOSE
510:         else
511:           super
512:         end
513:       end

SQLite doesn‘t support a NOT LIKE b, you need to use NOT (a LIKE b). It doesn‘t support xor or the extract function natively, so those have to be emulated.

[Source]

     # File lib/sequel/adapters/shared/sqlite.rb, line 517
517:       def complex_expression_sql_append(sql, op, args)
518:         case op
519:         when "NOT LIKE""NOT LIKE", "NOT ILIKE""NOT ILIKE"
520:           sql << NOT_SPACE
521:           complex_expression_sql_append(sql, (op == "NOT ILIKE""NOT ILIKE" ? :ILIKE : :LIKE), args)
522:         when :^
523:           sql << complex_expression_arg_pairs(args) do |a, b|
524:             a = literal(a)
525:             b = literal(b)
526:             "((~(#{a} & #{b})) & (#{a} | #{b}))"
527:           end
528:         when :extract
529:           part = args.at(0)
530:           raise(Sequel::Error, "unsupported extract argument: #{part.inspect}") unless format = EXTRACT_MAP[part]
531:           sql << EXTRACT_OPEN << format << COMMA
532:           literal_append(sql, args.at(1))
533:           sql << EXTRACT_CLOSE << (part == :second ? NUMERIC : INTEGER) << PAREN_CLOSE
534:         else
535:           super
536:         end
537:       end

SQLite has CURRENT_TIMESTAMP and related constants in UTC instead of in localtime, so convert those constants to local time.

[Source]

     # File lib/sequel/adapters/shared/sqlite.rb, line 541
541:       def constant_sql_append(sql, constant)
542:         if c = CONSTANT_MAP[constant]
543:           sql << c
544:         else
545:           super
546:         end
547:       end

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.

[Source]

     # File lib/sequel/adapters/shared/sqlite.rb, line 552
552:       def delete
553:         @opts[:where] ? super : where(1=>1).delete
554:       end

Return an array of strings specifying a query explanation for a SELECT of the current dataset. Currently, the options are ignore, but it accepts options to be compatible with other adapters.

[Source]

     # File lib/sequel/adapters/shared/sqlite.rb, line 559
559:       def explain(opts=nil)
560:         # Load the PrettyTable class, needed for explain output
561:         Sequel.extension(:_pretty_table) unless defined?(Sequel::PrettyTable)
562: 
563:         ds = db.send(:metadata_dataset).clone(:sql=>"EXPLAIN #{select_sql}")
564:         rows = ds.all
565:         Sequel::PrettyTable.string(rows, ds.columns)
566:       end

HAVING requires GROUP BY on SQLite

[Source]

     # File lib/sequel/adapters/shared/sqlite.rb, line 569
569:       def having(*cond)
570:         raise(InvalidOperation, "Can only specify a HAVING clause on a grouped dataset") unless @opts[:group]
571:         super
572:       end

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

[Source]

     # File lib/sequel/adapters/shared/sqlite.rb, line 575
575:       def quoted_identifier_append(sql, c)
576:         sql << BACKTICK << c.to_s.gsub(BACKTICK_RE, DOUBLE_BACKTICK) << BACKTICK
577:       end

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.

[Source]

     # File lib/sequel/adapters/shared/sqlite.rb, line 583
583:       def select(*cols)
584:         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)})
585:           super(*cols.map{|c| alias_qualified_column(c)})
586:         else
587:           super
588:         end
589:       end

SQLite does not support INTERSECT ALL or EXCEPT ALL

[Source]

     # File lib/sequel/adapters/shared/sqlite.rb, line 592
592:       def supports_intersect_except_all?
593:         false
594:       end

SQLite does not support IS TRUE

[Source]

     # File lib/sequel/adapters/shared/sqlite.rb, line 597
597:       def supports_is_true?
598:         false
599:       end

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

[Source]

     # File lib/sequel/adapters/shared/sqlite.rb, line 602
602:       def supports_multiple_column_in?
603:         false
604:       end

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.

[Source]

     # File lib/sequel/adapters/shared/sqlite.rb, line 609
609:       def supports_timestamp_timezones?
610:         db.use_timestamp_timezones?
611:       end

SQLite cannot use WHERE ‘t’.

[Source]

     # File lib/sequel/adapters/shared/sqlite.rb, line 614
614:       def supports_where_true?
615:         false
616:       end

[Validate]