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
Constants
ADAPTER_NAME = 'PostgreSQL'.freeze
NATIVE_DATABASE_TYPES = { :primary_key => "serial primary key".freeze, :string => { :name => "character varying", :limit => 255 }, :text => { :name => "text" }, :integer => { :name => "integer" }, :float => { :name => "float" }, :decimal => { :name => "decimal" }, :datetime => { :name => "timestamp" }, :timestamp => { :name => "timestamp" }, :time => { :name => "time" }, :date => { :name => "date" }, :binary => { :name => "bytea" }, :boolean => { :name => "boolean" }, :xml => { :name => "xml" }
Public Class methods
new(connection, logger, connection_parameters, config)

Initializes and connects a PostgreSQL adapter.

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 213
213:       def initialize(connection, logger, connection_parameters, config)
214:         super(connection, logger)
215:         @connection_parameters, @config = connection_parameters, config
216: 
217:         connect
218:       end
Public Instance methods
active?()

Is this connection alive and ready for queries?

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 221
221:       def active?
222:         if @connection.respond_to?(:status)
223:           @connection.status == PGconn::CONNECTION_OK
224:         else
225:           # We're asking the driver, not ActiveRecord, so use @connection.query instead of #query
226:           @connection.query 'SELECT 1'
227:           true
228:         end
229:       # postgres-pr raises a NoMethodError when querying if no connection is available.
230:       rescue PGError, NoMethodError
231:         false
232:       end
adapter_name()

Returns ‘PostgreSQL’ as adapter name for identification purposes.

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 208
208:       def adapter_name
209:         ADAPTER_NAME
210:       end
add_column(table_name, column_name, type, options = {})

Adds a new column to the named table. See TableDefinition#column for details of the options you can use.

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 815
815:       def add_column(table_name, column_name, type, options = {})
816:         default = options[:default]
817:         notnull = options[:null] == false
818: 
819:         # Add the column.
820:         execute("ALTER TABLE #{quote_table_name(table_name)} ADD COLUMN #{quote_column_name(column_name)} #{type_to_sql(type, options[:limit], options[:precision], options[:scale])}")
821: 
822:         change_column_default(table_name, column_name, default) if options_include_default?(options)
823:         change_column_null(table_name, column_name, false, default) if notnull
824:       end
begin_db_transaction()

Begins a transaction.

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 535
535:       def begin_db_transaction
536:         execute "BEGIN"
537:       end
change_column(table_name, column_name, type, options = {})

Changes the column of a table.

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 827
827:       def change_column(table_name, column_name, type, options = {})
828:         quoted_table_name = quote_table_name(table_name)
829: 
830:         begin
831:           execute "ALTER TABLE #{quoted_table_name} ALTER COLUMN #{quote_column_name(column_name)} TYPE #{type_to_sql(type, options[:limit], options[:precision], options[:scale])}"
832:         rescue ActiveRecord::StatementInvalid => e
833:           raise e if postgresql_version > 80000
834:           # This is PostgreSQL 7.x, so we have to use a more arcane way of doing it.
835:           begin
836:             begin_db_transaction
837:             tmp_column_name = "#{column_name}_ar_tmp"
838:             add_column(table_name, tmp_column_name, type, options)
839:             execute "UPDATE #{quoted_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])})"
840:             remove_column(table_name, column_name)
841:             rename_column(table_name, tmp_column_name, column_name)
842:             commit_db_transaction
843:           rescue
844:             rollback_db_transaction
845:           end
846:         end
847: 
848:         change_column_default(table_name, column_name, options[:default]) if options_include_default?(options)
849:         change_column_null(table_name, column_name, options[:null], options[:default]) if options.key?(:null)
850:       end
change_column_default(table_name, column_name, default)

Changes the default value of a table column.

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 853
853:       def change_column_default(table_name, column_name, default)
854:         execute "ALTER TABLE #{quote_table_name(table_name)} ALTER COLUMN #{quote_column_name(column_name)} SET DEFAULT #{quote(default)}"
855:       end
change_column_null(table_name, column_name, null, default = nil)

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 857
857:       def change_column_null(table_name, column_name, null, default = nil)
858:         unless null || default.nil?
859:           execute("UPDATE #{quote_table_name(table_name)} SET #{quote_column_name(column_name)}=#{quote(default)} WHERE #{quote_column_name(column_name)} IS NULL")
860:         end
861:         execute("ALTER TABLE #{quote_table_name(table_name)} ALTER #{quote_column_name(column_name)} #{null ? 'DROP' : 'SET'} NOT NULL")
862:       end
client_min_messages()

Returns the current client message level.

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 715
715:       def client_min_messages
716:         query('SHOW client_min_messages')[0][0]
717:       end
client_min_messages=(level)

Set the client message level.

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 720
720:       def client_min_messages=(level)
721:         execute("SET client_min_messages TO '#{level}'")
722:       end
columns(table_name, name = nil)

Returns the list of all column definitions for a table.

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 676
676:       def columns(table_name, name = nil)
677:         # Limit, precision, and scale are all handled by the superclass.
678:         column_definitions(table_name).collect do |name, type, default, notnull|
679:           PostgreSQLColumn.new(name, default, type, notnull == 'f')
680:         end
681:       end
commit_db_transaction()

Commits a transaction.

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 540
540:       def commit_db_transaction
541:         execute "COMMIT"
542:       end
create_database(name, options = {})

Create a new PostgreSQL database. Options include :owner, :template, :encoding, :tablespace, and :connection_limit (note that MySQL uses :charset while PostgreSQL uses :encoding).

Example: 

  create_database config[:database], config
  create_database 'foo_development', :encoding => 'unicode'

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 583
583:       def create_database(name, options = {})
584:         options = options.reverse_merge(:encoding => "utf8")
585: 
586:         option_string = options.symbolize_keys.sum do |key, value|
587:           case key
588:           when :owner
589:             " OWNER = \"#{value}\""
590:           when :template
591:             " TEMPLATE = \"#{value}\""
592:           when :encoding
593:             " ENCODING = '#{value}'"
594:           when :tablespace
595:             " TABLESPACE = \"#{value}\""
596:           when :connection_limit
597:             " CONNECTION LIMIT = #{value}"
598:           else
599:             ""
600:           end
601:         end
602: 
603:         execute "CREATE DATABASE #{quote_table_name(name)}#{option_string}"
604:       end
create_savepoint()

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 557
557:       def create_savepoint
558:         execute("SAVEPOINT #{current_savepoint_name}")
559:       end
current_database()

Returns the current database name.

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 684
684:       def current_database
685:         query('select current_database()')[0][0]
686:       end
disconnect!()

Close the connection.

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 246
246:       def disconnect!
247:         @connection.close rescue nil
248:       end
encoding()

Returns the current database encoding format.

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 689
689:       def encoding
690:         query("SELECT pg_encoding_to_char(pg_database.encoding) FROM pg_database\nWHERE pg_database.datname LIKE '\#{current_database}'\n")[0][0]
691:       end
escape_bytea(original_value)

Escapes binary strings for bytea input to the database.

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 293
293:       def escape_bytea(original_value)
294:         if @connection.respond_to?(:escape_bytea)
295:           self.class.instance_eval do
296:             define_method(:escape_bytea) do |value|
297:               @connection.escape_bytea(value) if value
298:             end
299:           end
300:         elsif PGconn.respond_to?(:escape_bytea)
301:           self.class.instance_eval do
302:             define_method(:escape_bytea) do |value|
303:               PGconn.escape_bytea(value) if value
304:             end
305:           end
306:         else
307:           self.class.instance_eval do
308:             define_method(:escape_bytea) do |value|
309:               if value
310:                 result = ''
311:                 value.each_byte { |c| result << sprintf('\\\\%03o', c) }
312:                 result
313:               end
314:             end
315:           end
316:         end
317:         escape_bytea(original_value)
318:       end
execute(sql, name = nil)

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

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 519
519:       def execute(sql, name = nil)
520:         log(sql, name) do
521:           if @async
522:             @connection.async_exec(sql)
523:           else
524:             @connection.exec(sql)
525:           end
526:         end
527:       end
index_name_length()

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 873
873:       def index_name_length
874:         63
875:       end
indexes(table_name, name = nil)

Returns the list of all indexes for a table.

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 635
635:       def indexes(table_name, name = nil)
636:          schemas = schema_search_path.split(/,/).map { |p| quote(p) }.join(',')
637:          result = query("SELECT distinct i.relname, d.indisunique, d.indkey, t.oid\nFROM pg_class t, pg_class i, pg_index d\nWHERE i.relkind = 'i'\nAND d.indexrelid = i.oid\nAND d.indisprimary = 'f'\nAND t.oid = d.indrelid\nAND t.relname = '\#{table_name}'\nAND i.relnamespace IN (SELECT oid FROM pg_namespace WHERE nspname IN (\#{schemas}) )\nORDER BY i.relname\n", name)
638: 
639: 
640:         indexes = []
641: 
642:         indexes = result.map do |row|
643:           index_name = row[0]
644:           unique = row[1] == 't'
645:           indkey = row[2].split(" ")
646:           oid = row[3]
647: 
648:           columns = query("SELECT a.attname, a.attnum\nFROM pg_attribute a\nWHERE a.attrelid = \#{oid}\nAND a.attnum IN (\#{indkey.join(\",\")})\n", "Columns for index #{row[0]} on #{table_name}").inject({}) {|attlist, r| attlist[r[1]] = r[0]; attlist}
649: 
650:           column_names = indkey.map {|attnum| columns[attnum] }
651:           IndexDefinition.new(table_name, index_name, unique, column_names)
652: 
653:         end
654: 
655:         indexes
656:       end
insert(sql, name = nil, pk = nil, id_value = nil, sequence_name = nil)

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

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 452
452:       def insert(sql, name = nil, pk = nil, id_value = nil, sequence_name = nil)
453:         # Extract the table from the insert sql. Yuck.
454:         table = sql.split(" ", 4)[2].gsub('"', '')
455: 
456:         # Try an insert with 'returning id' if available (PG >= 8.2)
457:         if supports_insert_with_returning?
458:           pk, sequence_name = *pk_and_sequence_for(table) unless pk
459:           if pk
460:             id = select_value("#{sql} RETURNING #{quote_column_name(pk)}")
461:             clear_query_cache
462:             return id
463:           end
464:         end
465: 
466:         # Otherwise, insert then grab last_insert_id.
467:         if insert_id = super
468:           insert_id
469:         else
470:           # If neither pk nor sequence name is given, look them up.
471:           unless pk || sequence_name
472:             pk, sequence_name = *pk_and_sequence_for(table)
473:           end
474: 
475:           # If a pk is given, fallback to default sequence name.
476:           # Don't fetch last insert id for a table without a pk.
477:           if pk && sequence_name ||= default_sequence_name(table, pk)
478:             last_insert_id(table, sequence_name)
479:           end
480:         end
481:       end
outside_transaction?()

The ruby-pg driver supports inspecting the transaction status, while the ruby-postgres driver does not.

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 552
552:         def outside_transaction?
553:           @connection.transaction_status == PGconn::PQTRANS_IDLE
554:         end
primary_key(table)

Returns just a table‘s primary key

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 803
803:       def primary_key(table)
804:         pk_and_sequence = pk_and_sequence_for(table)
805:         pk_and_sequence && pk_and_sequence.first
806:       end
quote_table_name(name)

Checks the following cases:

  • table_name
  • "table.name"
  • schema_name.table_name
  • schema_name."table.name"
  • "schema.name".table_name
  • "schema.name"."table.name"

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 397
397:       def quote_table_name(name)
398:         schema, name_part = extract_pg_identifier_from_name(name.to_s)
399: 
400:         unless name_part
401:           quote_column_name(schema)
402:         else
403:           table_name, name_part = extract_pg_identifier_from_name(name_part)
404:           "#{quote_column_name(schema)}.#{quote_column_name(table_name)}"
405:         end
406:       end
reconnect!()

Close then reopen the connection.

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 235
235:       def reconnect!
236:         if @connection.respond_to?(:reset)
237:           @connection.reset
238:           configure_connection
239:         else
240:           disconnect!
241:           connect
242:         end
243:       end
release_savepoint()

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 565
565:       def release_savepoint
566:         execute("RELEASE SAVEPOINT #{current_savepoint_name}")
567:       end
rename_column(table_name, column_name, new_column_name)

Renames a column in a table.

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 865
865:       def rename_column(table_name, column_name, new_column_name)
866:         execute "ALTER TABLE #{quote_table_name(table_name)} RENAME COLUMN #{quote_column_name(column_name)} TO #{quote_column_name(new_column_name)}"
867:       end
rename_table(name, new_name)

Renames a table.

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 809
809:       def rename_table(name, new_name)
810:         execute "ALTER TABLE #{quote_table_name(name)} RENAME TO #{quote_table_name(new_name)}"
811:       end
rollback_db_transaction()

Aborts a transaction.

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 545
545:       def rollback_db_transaction
546:         execute "ROLLBACK"
547:       end
rollback_to_savepoint()

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 561
561:       def rollback_to_savepoint
562:         execute("ROLLBACK TO SAVEPOINT #{current_savepoint_name}")
563:       end
schema_search_path()

Returns the active schema search path.

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 710
710:       def schema_search_path
711:         @schema_search_path ||= query('SHOW search_path')[0][0]
712:       end
schema_search_path=(schema_csv)

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.

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 702
702:       def schema_search_path=(schema_csv)
703:         if schema_csv
704:           execute "SET search_path TO #{schema_csv}"
705:           @schema_search_path = schema_csv
706:         end
707:       end
select_rows(sql, name = nil)

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

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 447
447:       def select_rows(sql, name = nil)
448:         select_raw(sql, name).last
449:       end
set_standard_conforming_strings()

Enable standard-conforming strings if available.

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 265
265:       def set_standard_conforming_strings
266:         old, self.client_min_messages = client_min_messages, 'panic'
267:         execute('SET standard_conforming_strings = on') rescue nil
268:       ensure
269:         self.client_min_messages = old
270:       end
supports_ddl_transactions?()

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 276
276:       def supports_ddl_transactions?
277:         true
278:       end
supports_insert_with_returning?()

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 272
272:       def supports_insert_with_returning?
273:         postgresql_version >= 80200
274:       end
supports_migrations?()

Does PostgreSQL support migrations?

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 255
255:       def supports_migrations?
256:         true
257:       end
supports_savepoints?()

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 280
280:       def supports_savepoints?
281:         true
282:       end
table_alias_length()

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

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 286
286:       def table_alias_length
287:         @table_alias_length ||= (postgresql_version >= 80000 ? query('SHOW max_identifier_length')[0][0].to_i : 63)
288:       end
tables(name = nil)

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

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 624
624:       def tables(name = nil)
625:         schemas = schema_search_path.split(/,/).map { |p| quote(p) }.join(',')
626:         query("SELECT tablename\nFROM pg_tables\nWHERE schemaname IN (\#{schemas})\n", name).map { |row| row[0] }
627:       end
type_to_sql(type, limit = nil, precision = nil, scale = nil)

Maps logical Rails types to PostgreSQL-specific data types.

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 878
878:       def type_to_sql(type, limit = nil, precision = nil, scale = nil)
879:         return super unless type.to_s == 'integer'
880: 
881:         case limit
882:           when 1..2;      'smallint'
883:           when 3..4, nil; 'integer'
884:           when 5..8;      'bigint'
885:           else raise(ActiveRecordError, "No integer type has byte size #{limit}. Use a numeric with precision 0 instead.")
886:         end
887:       end
unescape_bytea(original_value)

Unescapes bytea output from a database to the binary string it represents. NOTE: This is NOT an inverse of escape_bytea! This is only to be used 

      on escaped binary output from database drive.

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 323
323:       def unescape_bytea(original_value)
324:         # In each case, check if the value actually is escaped PostgreSQL bytea output
325:         # or an unescaped Active Record attribute that was just written.
326:         if @connection.respond_to?(:unescape_bytea)
327:           self.class.instance_eval do
328:             define_method(:unescape_bytea) do |value|
329:               @connection.unescape_bytea(value) if value
330:             end
331:           end
332:         elsif PGconn.respond_to?(:unescape_bytea)
333:           self.class.instance_eval do
334:             define_method(:unescape_bytea) do |value|
335:               PGconn.unescape_bytea(value) if value
336:             end
337:           end
338:         else
339:           raise 'Your PostgreSQL connection does not support unescape_bytea. Try upgrading to pg 0.9.0 or later.'
340:         end
341:         unescape_bytea(original_value)
342:       end
update_sql(sql, name = nil)

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

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 530
530:       def update_sql(sql, name = nil)
531:         super.cmd_tuples
532:       end
Protected Instance methods
postgresql_version()

Returns the version of the connected PostgreSQL version.

[ show source ]

     # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 926
926:         def postgresql_version
927:           @postgresql_version ||=
928:             if @connection.respond_to?(:server_version)
929:               @connection.server_version
930:             else
931:               # Mimic PGconn.server_version behavior
932:               begin
933:                 query('SELECT version()')[0][0] =~ /PostgreSQL (\d+)\.(\d+)\.(\d+)/
934:                 ($1.to_i * 10000) + ($2.to_i * 100) + $3.to_i
935:               rescue
936:                 0
937:               end
938:             end
939:         end