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

Instance methods for datasets that connect to an SQLite database

### Methods

complex_expression_sql_append constant_sql_append delete explain having quoted_identifier_append select supports_intersect_except_all? supports_is_true? supports_multiple_column_in? supports_timestamp_timezones? supports_where_true?

### 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
EXRACT_CLOSE | = | ') AS '.freeze
NUMERIC | = | 'NUMERIC'.freeze
INTEGER | = | 'INTEGER'.freeze
BACKTICK | = | '`'.freeze
BLOB_START | = | "X'".freeze
HSTAR | = | "H*".freeze

### Public Instance methods

complex_expression_sql_append(sql, op, args)

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 418
    418:       def complex_expression_sql_append(sql, op, args)
    419:         case op
    420:         when :~, '!~''!~', '~*''~*', '!~*''!~*'
    421:           raise Error, "SQLite does not support pattern matching via regular expressions"
    422:         when :ILIKE
    423:           super(sql, :LIKE, args.map{|a| SQL::Function.new(:upper, a)})
    424:         when "NOT LIKE""NOT LIKE", "NOT ILIKE""NOT ILIKE"
    425:           sql << NOT_SPACE
    426:           complex_expression_sql_append(sql, (op == "NOT ILIKE""NOT ILIKE" ? :ILIKE : :LIKE), args)
    427:         when :^
    428:           sql << complex_expression_arg_pairs(args) do |a, b|
    429:             a = literal(a)
    430:             b = literal(b)
    431:             "((~(#{a} & #{b})) & (#{a} | #{b}))"
    432:           end
    433:         when :extract
    434:           part = args.at(0)
    435:           raise(Sequel::Error, "unsupported extract argument: #{part.inspect}") unless format = EXTRACT_MAP[part]
    436:           sql << EXTRACT_OPEN << format << COMMA
    437:           literal_append(sql, args.at(1))
    438:           sql << EXRACT_CLOSE << (part == :second ? NUMERIC : INTEGER) << PAREN_CLOSE
    439:         else
    440:           super
    441:         end
    442:       end

constant_sql_append(sql, constant)

MSSQL doesn‘t support the SQL standard CURRENT_DATE or CURRENT_TIME

[Source]

         # File lib/sequel/adapters/shared/sqlite.rb, line 445
    445:       def constant_sql_append(sql, constant)
    446:         if c = CONSTANT_MAP[constant]
    447:           sql << c
    448:         else
    449:           super
    450:         end
    451:       end

delete()

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 456
    456:       def delete
    457:         @opts[:where] ? super : filter(1=>1).delete
    458:       end

explain()

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

[Source]

         # File lib/sequel/adapters/shared/sqlite.rb, line 462
    462:       def explain
    463:         db.send(:metadata_dataset).clone(:sql=>"EXPLAIN #{select_sql}").
    464:           map{|x| "#{x[:addr]}|#{x[:opcode]}|#{(1..5).map{|i| x[:"p#{i}"]}.join('|')}|#{x[:comment]}"}
    465:       end

having(*cond)

HAVING requires GROUP BY on SQLite

[Source]

         # File lib/sequel/adapters/shared/sqlite.rb, line 468
    468:       def having(*cond)
    469:         raise(InvalidOperation, "Can only specify a HAVING clause on a grouped dataset") unless @opts[:group]
    470:         super
    471:       end

quoted_identifier_append(sql, c)

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

[Source]

         # File lib/sequel/adapters/shared/sqlite.rb, line 474
    474:       def quoted_identifier_append(sql, c)
    475:         sql << BACKTICK << c.to_s << BACKTICK
    476:       end

select(*cols)

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 482
    482:       def select(*cols)
    483:         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)})
    484:           super(*cols.map{|c| alias_qualified_column(c)})
    485:         else
    486:           super
    487:         end
    488:       end

supports_intersect_except_all?()

SQLite does not support INTERSECT ALL or EXCEPT ALL

[Source]

         # File lib/sequel/adapters/shared/sqlite.rb, line 491
    491:       def supports_intersect_except_all?
    492:         false
    493:       end

supports_is_true?()

SQLite does not support IS TRUE

[Source]

         # File lib/sequel/adapters/shared/sqlite.rb, line 496
    496:       def supports_is_true?
    497:         false
    498:       end

supports_multiple_column_in?()

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

[Source]

         # File lib/sequel/adapters/shared/sqlite.rb, line 501
    501:       def supports_multiple_column_in?
    502:         false
    503:       end

supports_timestamp_timezones?()

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 508
    508:       def supports_timestamp_timezones?
    509:         db.use_timestamp_timezones?
    510:       end

supports_where_true?()

SQLite cannot use WHERE ‘t’.

[Source]

         # File lib/sequel/adapters/shared/sqlite.rb, line 513
    513:       def supports_where_true?
    514:         false
    515:       end

[Validate]