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

Instance methods for datasets that connect to an SQLite database

Methods

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}
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

Public Instance methods

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

[Source]

     # File lib/sequel/adapters/shared/sqlite.rb, line 435
435:       def complex_expression_sql_append(sql, op, args)
436:         case op
437:         when :~, '!~''!~', '~*''~*', '!~*''!~*'
438:           raise Error, "SQLite does not support pattern matching via regular expressions"
439:         when :ILIKE
440:           super(sql, :LIKE, args.map{|a| SQL::Function.new(:upper, a)})
441:         when "NOT LIKE""NOT LIKE", "NOT ILIKE""NOT ILIKE"
442:           sql << NOT_SPACE
443:           complex_expression_sql_append(sql, (op == "NOT ILIKE""NOT ILIKE" ? :ILIKE : :LIKE), args)
444:         when :^
445:           sql << complex_expression_arg_pairs(args) do |a, b|
446:             a = literal(a)
447:             b = literal(b)
448:             "((~(#{a} & #{b})) & (#{a} | #{b}))"
449:           end
450:         when :extract
451:           part = args.at(0)
452:           raise(Sequel::Error, "unsupported extract argument: #{part.inspect}") unless format = EXTRACT_MAP[part]
453:           sql << EXTRACT_OPEN << format << COMMA
454:           literal_append(sql, args.at(1))
455:           sql << EXTRACT_CLOSE << (part == :second ? NUMERIC : INTEGER) << PAREN_CLOSE
456:         else
457:           super
458:         end
459:       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 463
463:       def constant_sql_append(sql, constant)
464:         if c = CONSTANT_MAP[constant]
465:           sql << c
466:         else
467:           super
468:         end
469:       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 474
474:       def delete
475:         @opts[:where] ? super : where(1=>1).delete
476:       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 481
481:       def explain(opts=nil)
482:         # Load the PrettyTable class, needed for explain output
483:         Sequel.extension(:_pretty_table) unless defined?(Sequel::PrettyTable)
484: 
485:         ds = db.send(:metadata_dataset).clone(:sql=>"EXPLAIN #{select_sql}")
486:         rows = ds.all
487:         Sequel::PrettyTable.string(rows, ds.columns)
488:       end

HAVING requires GROUP BY on SQLite

[Source]

     # File lib/sequel/adapters/shared/sqlite.rb, line 491
491:       def having(*cond)
492:         raise(InvalidOperation, "Can only specify a HAVING clause on a grouped dataset") unless @opts[:group]
493:         super
494:       end

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

[Source]

     # File lib/sequel/adapters/shared/sqlite.rb, line 497
497:       def quoted_identifier_append(sql, c)
498:         sql << BACKTICK << c.to_s.gsub(BACKTICK_RE, DOUBLE_BACKTICK) << BACKTICK
499:       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 505
505:       def select(*cols)
506:         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)})
507:           super(*cols.map{|c| alias_qualified_column(c)})
508:         else
509:           super
510:         end
511:       end

SQLite does not support INTERSECT ALL or EXCEPT ALL

[Source]

     # File lib/sequel/adapters/shared/sqlite.rb, line 514
514:       def supports_intersect_except_all?
515:         false
516:       end

SQLite does not support IS TRUE

[Source]

     # File lib/sequel/adapters/shared/sqlite.rb, line 519
519:       def supports_is_true?
520:         false
521:       end

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

[Source]

     # File lib/sequel/adapters/shared/sqlite.rb, line 524
524:       def supports_multiple_column_in?
525:         false
526:       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 531
531:       def supports_timestamp_timezones?
532:         db.use_timestamp_timezones?
533:       end

SQLite cannot use WHERE ‘t’.

[Source]

     # File lib/sequel/adapters/shared/sqlite.rb, line 536
536:       def supports_where_true?
537:         false
538:       end

[Validate]