Class ActiveRecord::ConnectionAdapters::PostgreSQLAdapter
In: vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
Parent: AbstractAdapter

The PostgreSQL adapter works both with the native C (ruby.scripting.ca/postgres/) and the pure Ruby (available both as gem and from rubyforge.org/frs/?group_id=234&release_id=1944) drivers.

Options:

  • :host — Defaults to localhost
  • :port — Defaults to 5432
  • :username — Defaults to nothing
  • :password — Defaults to nothing
  • :database — The name of the database. No default, must be provided.
  • :schema_search_path — An optional schema search path for the connection given as a string of comma-separated schema names. This is backward-compatible with the :schema_order option.
  • :encoding — An optional client encoding that is used in a SET client_encoding TO <encoding> call on the connection.
  • :min_messages — An optional client min messages that is used in a SET client_min_messages TO <min_messages> call on the connection.
  • :allow_concurrency — If true, use async query methods so Ruby threads don‘t deadlock; otherwise, use blocking query methods.

Methods

Public Class methods

Initializes and connects a PostgreSQL adapter.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 233
233:       def initialize(connection, logger, connection_parameters, config)
234:         super(connection, logger)
235:         @connection_parameters, @config = connection_parameters, config
236: 
237:         connect
238:       end

Public Instance methods

Is this connection alive and ready for queries?

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 241
241:       def active?
242:         if @connection.respond_to?(:status)
243:           @connection.status == PGconn::CONNECTION_OK
244:         else
245:           # We're asking the driver, not ActiveRecord, so use @connection.query instead of #query
246:           @connection.query 'SELECT 1'
247:           true
248:         end
249:       # postgres-pr raises a NoMethodError when querying if no connection is available.
250:       rescue PGError, NoMethodError
251:         false
252:       end

Returns ‘PostgreSQL’ as adapter name for identification purposes.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 228
228:       def adapter_name
229:         'PostgreSQL'
230:       end

Adds a column to a table.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 594
594:       def add_column(table_name, column_name, type, options = {})
595:         default = options[:default]
596:         notnull = options[:null] == false
597: 
598:         # Add the column.
599:         execute("ALTER TABLE #{table_name} ADD COLUMN #{quote_column_name(column_name)} #{type_to_sql(type, options[:limit])}")
600: 
601:         change_column_default(table_name, column_name, default) if options_include_default?(options)
602:         change_column_null(table_name, column_name, false, default) if notnull
603:       end

Begins a transaction.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 422
422:       def begin_db_transaction
423:         execute "BEGIN"
424:       end

Changes the column of a table.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 606
606:       def change_column(table_name, column_name, type, options = {})
607:         begin
608:           execute "ALTER TABLE #{table_name} ALTER COLUMN #{quote_column_name(column_name)} TYPE #{type_to_sql(type, options[:limit], options[:precision], options[:scale])}"
609:         rescue ActiveRecord::StatementInvalid
610:           # This is PostgreSQL 7.x, so we have to use a more arcane way of doing it.
611:           begin_db_transaction
612:           tmp_column_name = "#{column_name}_ar_tmp"
613:           add_column(table_name, tmp_column_name, type, options)
614:           execute "UPDATE #{table_name} SET #{quote_column_name(tmp_column_name)} = CAST(#{quote_column_name(column_name)} AS #{type_to_sql(type, options[:limit], options[:precision], options[:scale])})"
615:           remove_column(table_name, column_name)
616:           rename_column(table_name, tmp_column_name, column_name)
617:           commit_db_transaction
618:         end
619: 
620:         change_column_default(table_name, column_name, options[:default]) if options_include_default?(options)
621:         change_column_null(table_name, column_name, options[:null], options[:default]) if options.key?(:null)
622:       end

Changes the default value of a table column.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 625
625:       def change_column_default(table_name, column_name, default)
626:         execute "ALTER TABLE #{table_name} ALTER COLUMN #{quote_column_name(column_name)} SET DEFAULT #{quote(default)}"
627:       end

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 629
629:       def change_column_null(table_name, column_name, null, default = nil)
630:         unless null || default.nil?
631:           execute("UPDATE #{table_name} SET #{quote_column_name(column_name)}=#{quote(default)} WHERE #{quote_column_name(column_name)} IS NULL")
632:         end
633:         execute("ALTER TABLE #{table_name} ALTER #{quote_column_name(column_name)} #{null ? 'DROP' : 'SET'} NOT NULL")
634:       end

Returns the current client message level.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 510
510:       def client_min_messages
511:         query('SHOW client_min_messages')[0][0]
512:       end

Set the client message level.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 515
515:       def client_min_messages=(level)
516:         execute("SET client_min_messages TO '#{level}'")
517:       end

Returns the list of all column definitions for a table.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 485
485:       def columns(table_name, name = nil)
486:         # Limit, precision, and scale are all handled by the superclass.
487:         column_definitions(table_name).collect do |name, type, default, notnull|
488:           PostgreSQLColumn.new(name, default, type, notnull == 'f')
489:         end
490:       end

Commits a transaction.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 427
427:       def commit_db_transaction
428:         execute "COMMIT"
429:       end

Close the connection.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 266
266:       def disconnect!
267:         @connection.close rescue nil
268:       end

Executes an SQL statement, returning a PGresult object on success or raising a PGError exception otherwise.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 406
406:       def execute(sql, name = nil)
407:         log(sql, name) do
408:           if @async
409:             @connection.async_exec(sql)
410:           else
411:             @connection.exec(sql)
412:           end
413:         end
414:       end

Returns the list of all indexes for a table.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 450
450:       def indexes(table_name, name = nil)
451:         result = query("SELECT i.relname, d.indisunique, a.attname\nFROM pg_class t, pg_class i, pg_index d, pg_attribute a\nWHERE i.relkind = 'i'\nAND d.indexrelid = i.oid\nAND d.indisprimary = 'f'\nAND t.oid = d.indrelid\nAND t.relname = '\#{table_name}'\nAND a.attrelid = t.oid\nAND ( d.indkey[0]=a.attnum OR d.indkey[1]=a.attnum\nOR d.indkey[2]=a.attnum OR d.indkey[3]=a.attnum\nOR d.indkey[4]=a.attnum OR d.indkey[5]=a.attnum\nOR d.indkey[6]=a.attnum OR d.indkey[7]=a.attnum\nOR d.indkey[8]=a.attnum OR d.indkey[9]=a.attnum )\nORDER BY i.relname\n", name)
452: 
453:         current_index = nil
454:         indexes = []
455: 
456:         result.each do |row|
457:           if current_index != row[0]
458:             indexes << IndexDefinition.new(table_name, row[0], row[1] == "t", [])
459:             current_index = row[0]
460:           end
461: 
462:           indexes.last.columns << row[2]
463:         end
464: 
465:         indexes
466:       end

Executes an INSERT query and returns the new record‘s ID

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 388
388:       def insert(sql, name = nil, pk = nil, id_value = nil, sequence_name = nil)
389:         table = sql.split(" ", 4)[2]
390:         super || last_insert_id(table, sequence_name || default_sequence_name(table, pk))
391:       end

Close then reopen the connection.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 255
255:       def reconnect!
256:         if @connection.respond_to?(:reset)
257:           @connection.reset
258:           configure_connection
259:         else
260:           disconnect!
261:           connect
262:         end
263:       end

Drops an index from a table.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 642
642:       def remove_index(table_name, options = {})
643:         execute "DROP INDEX #{index_name(table_name, options)}"
644:       end

Renames a column in a table.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 637
637:       def rename_column(table_name, column_name, new_column_name)
638:         execute "ALTER TABLE #{table_name} RENAME COLUMN #{quote_column_name(column_name)} TO #{quote_column_name(new_column_name)}"
639:       end

Renames a table.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 589
589:       def rename_table(name, new_name)
590:         execute "ALTER TABLE #{name} RENAME TO #{new_name}"
591:       end

Aborts a transaction.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 432
432:       def rollback_db_transaction
433:         execute "ROLLBACK"
434:       end

Returns the active schema search path.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 505
505:       def schema_search_path
506:         @schema_search_path ||= query('SHOW search_path')[0][0]
507:       end

Sets the schema search path to a string of comma-separated schema names. Names beginning with $ have to be quoted (e.g. $user => ’$user’). See: www.postgresql.org/docs/current/static/ddl-schemas.html

This should be not be called manually but set in database.yml.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 497
497:       def schema_search_path=(schema_csv)
498:         if schema_csv
499:           execute "SET search_path TO #{schema_csv}"
500:           @schema_search_path = schema_csv
501:         end
502:       end

Executes a SELECT query and returns an array of rows. Each row is an array of field values.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 383
383:       def select_rows(sql, name = nil)
384:         select_raw(sql, name).last
385:       end

Does PostgreSQL support migrations?

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 288
288:       def supports_migrations?
289:         true
290:       end

Does PostgreSQL support standard conforming strings?

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 293
293:       def supports_standard_conforming_strings?
294:         # Temporarily set the client message level above error to prevent unintentional
295:         # error messages in the logs when working on a PostgreSQL database server that
296:         # does not support standard conforming strings.
297:         client_min_messages_old = client_min_messages
298:         self.client_min_messages = 'panic'
299: 
300:         # postgres-pr does not raise an exception when client_min_messages is set higher
301:         # than error and "SHOW standard_conforming_strings" fails, but returns an empty
302:         # PGresult instead.
303:         has_support = execute('SHOW standard_conforming_strings')[0][0] rescue false
304:         self.client_min_messages = client_min_messages_old
305:         has_support
306:       end

Returns the configured supported identifier length supported by PostgreSQL, or report the default of 63 on PostgreSQL 7.x.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 310
310:       def table_alias_length
311:         @table_alias_length ||= (postgresql_version >= 80000 ? query('SHOW max_identifier_length')[0][0].to_i : 63)
312:       end

Returns the list of all tables in the schema search path or a specified schema.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 439
439:       def tables(name = nil)
440:         schemas = schema_search_path.split(/,/).map { |p| quote(p) }.join(',')
441:         query("SELECT tablename\nFROM pg_tables\nWHERE schemaname IN (\#{schemas})\n", name).map { |row| row[0] }
442:       end

Maps logical Rails types to PostgreSQL-specific data types.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 647
647:       def type_to_sql(type, limit = nil, precision = nil, scale = nil)
648:         return super unless type.to_s == 'integer'
649: 
650:         if limit.nil? || limit == 4
651:           'integer'
652:         elsif limit < 4
653:           'smallint'
654:         else
655:           'bigint'
656:         end
657:       end

Executes an UPDATE query and returns the number of affected tuples.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 417
417:       def update_sql(sql, name = nil)
418:         super.cmdtuples
419:       end

Protected Instance methods

Returns the version of the connected PostgreSQL version.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 696
696:         def postgresql_version
697:           @postgresql_version ||=
698:             if @connection.respond_to?(:server_version)
699:               @connection.server_version
700:             else
701:               # Mimic PGconn.server_version behavior
702:               begin
703:                 query('SELECT version()')[0][0] =~ /PostgreSQL (\d+)\.(\d+)\.(\d+)/
704:                 ($1.to_i * 10000) + ($2.to_i * 100) + $3.to_i
705:               rescue
706:                 0
707:               end
708:             end
709:         end

[Validate]