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" }
Public Class methods
new(connection, logger, connection_parameters, config)

Initializes and connects a PostgreSQL adapter.

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 206
206:       def initialize(connection, logger, connection_parameters, config)
207:         super(connection, logger)
208:         @connection_parameters, @config = connection_parameters, config
209: 
210:         connect
211:       end
Public Instance methods
active?()

Is this connection alive and ready for queries?

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 214
214:       def active?
215:         if @connection.respond_to?(:status)
216:           @connection.status == PGconn::CONNECTION_OK
217:         else
218:           # We're asking the driver, not ActiveRecord, so use @connection.query instead of #query
219:           @connection.query 'SELECT 1'
220:           true
221:         end
222:       # postgres-pr raises a NoMethodError when querying if no connection is available.
223:       rescue PGError, NoMethodError
224:         false
225:       end
adapter_name()

Returns ‘PostgreSQL’ as adapter name for identification purposes.

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 201
201:       def adapter_name
202:         ADAPTER_NAME
203:       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 vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 827
827:       def add_column(table_name, column_name, type, options = {})
828:         default = options[:default]
829:         notnull = options[:null] == false
830: 
831:         # Add the column.
832:         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])}")
833: 
834:         change_column_default(table_name, column_name, default) if options_include_default?(options)
835:         change_column_null(table_name, column_name, false, default) if notnull
836:       end
begin_db_transaction()

Begins a transaction.

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 553
553:       def begin_db_transaction
554:         execute "BEGIN"
555:       end
change_column(table_name, column_name, type, options = {})

Changes the column of a table.

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 839
839:       def change_column(table_name, column_name, type, options = {})
840:         quoted_table_name = quote_table_name(table_name)
841: 
842:         begin
843:           execute "ALTER TABLE #{quoted_table_name} ALTER COLUMN #{quote_column_name(column_name)} TYPE #{type_to_sql(type, options[:limit], options[:precision], options[:scale])}"
844:         rescue ActiveRecord::StatementInvalid => e
845:           raise e if postgresql_version > 80000
846:           # This is PostgreSQL 7.x, so we have to use a more arcane way of doing it.
847:           begin
848:             begin_db_transaction
849:             tmp_column_name = "#{column_name}_ar_tmp"
850:             add_column(table_name, tmp_column_name, type, options)
851:             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])})"
852:             remove_column(table_name, column_name)
853:             rename_column(table_name, tmp_column_name, column_name)
854:             commit_db_transaction
855:           rescue
856:             rollback_db_transaction
857:           end
858:         end
859: 
860:         change_column_default(table_name, column_name, options[:default]) if options_include_default?(options)
861:         change_column_null(table_name, column_name, options[:null], options[:default]) if options.key?(:null)
862:       end
change_column_default(table_name, column_name, default)

Changes the default value of a table column.

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 865
865:       def change_column_default(table_name, column_name, default)
866:         execute "ALTER TABLE #{quote_table_name(table_name)} ALTER COLUMN #{quote_column_name(column_name)} SET DEFAULT #{quote(default)}"
867:       end
change_column_null(table_name, column_name, null, default = nil)

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 869
869:       def change_column_null(table_name, column_name, null, default = nil)
870:         unless null || default.nil?
871:           execute("UPDATE #{quote_table_name(table_name)} SET #{quote_column_name(column_name)}=#{quote(default)} WHERE #{quote_column_name(column_name)} IS NULL")
872:         end
873:         execute("ALTER TABLE #{quote_table_name(table_name)} ALTER #{quote_column_name(column_name)} #{null ? 'DROP' : 'SET'} NOT NULL")
874:       end
client_min_messages()

Returns the current client message level.

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 733
733:       def client_min_messages
734:         query('SHOW client_min_messages')[0][0]
735:       end
client_min_messages=(level)

Set the client message level.

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 738
738:       def client_min_messages=(level)
739:         execute("SET client_min_messages TO '#{level}'")
740:       end
columns(table_name, name = nil)

Returns the list of all column definitions for a table.

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 694
694:       def columns(table_name, name = nil)
695:         # Limit, precision, and scale are all handled by the superclass.
696:         column_definitions(table_name).collect do |name, type, default, notnull|
697:           PostgreSQLColumn.new(name, default, type, notnull == 'f')
698:         end
699:       end
commit_db_transaction()

Commits a transaction.

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 558
558:       def commit_db_transaction
559:         execute "COMMIT"
560:       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 vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 601
601:       def create_database(name, options = {})
602:         options = options.reverse_merge(:encoding => "utf8")
603: 
604:         option_string = options.symbolize_keys.sum do |key, value|
605:           case key
606:           when :owner
607:             " OWNER = \"#{value}\""
608:           when :template
609:             " TEMPLATE = \"#{value}\""
610:           when :encoding
611:             " ENCODING = '#{value}'"
612:           when :tablespace
613:             " TABLESPACE = \"#{value}\""
614:           when :connection_limit
615:             " CONNECTION LIMIT = #{value}"
616:           else
617:             ""
618:           end
619:         end
620: 
621:         execute "CREATE DATABASE #{quote_table_name(name)}#{option_string}"
622:       end
create_savepoint()

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 575
575:       def create_savepoint
576:         execute("SAVEPOINT #{current_savepoint_name}")
577:       end
current_database()

Returns the current database name.

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 702
702:       def current_database
703:         query('select current_database()')[0][0]
704:       end
disconnect!()

Close the connection.

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 239
239:       def disconnect!
240:         @connection.close rescue nil
241:       end
encoding()

Returns the current database encoding format.

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 707
707:       def encoding
708:         query("SELECT pg_encoding_to_char(pg_database.encoding) FROM pg_database\nWHERE pg_database.datname LIKE '\#{current_database}'\n")[0][0]
709:       end
escape_bytea(value)

Escapes binary strings for bytea input to the database.

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 289
289:       def escape_bytea(value)
290:         if @connection.respond_to?(:escape_bytea)
291:           self.class.instance_eval do
292:             define_method(:escape_bytea) do |value|
293:               @connection.escape_bytea(value) if value
294:             end
295:           end
296:         elsif PGconn.respond_to?(:escape_bytea)
297:           self.class.instance_eval do
298:             define_method(:escape_bytea) do |value|
299:               PGconn.escape_bytea(value) if value
300:             end
301:           end
302:         else
303:           self.class.instance_eval do
304:             define_method(:escape_bytea) do |value|
305:               if value
306:                 result = ''
307:                 value.each_byte { |c| result << sprintf('\\\\%03o', c) }
308:                 result
309:               end
310:             end
311:           end
312:         end
313:         escape_bytea(value)
314:       end
execute(sql, name = nil)

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

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 537
537:       def execute(sql, name = nil)
538:         log(sql, name) do
539:           if @async
540:             @connection.async_exec(sql)
541:           else
542:             @connection.exec(sql)
543:           end
544:         end
545:       end
indexes(table_name, name = nil)

Returns the list of all indexes for a table.

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 653
653:       def indexes(table_name, name = nil)
654:          schemas = schema_search_path.split(/,/).map { |p| quote(p) }.join(',')
655:          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)
656: 
657: 
658:         indexes = []
659: 
660:         indexes = result.map do |row|
661:           index_name = row[0]
662:           unique = row[1] == 't'
663:           indkey = row[2].split(" ")
664:           oid = row[3]
665: 
666:           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}
667: 
668:           column_names = indkey.map {|attnum| columns[attnum] }
669:           IndexDefinition.new(table_name, index_name, unique, column_names)
670: 
671:         end
672: 
673:         indexes
674:       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 vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 470
470:       def insert(sql, name = nil, pk = nil, id_value = nil, sequence_name = nil)
471:         # Extract the table from the insert sql. Yuck.
472:         table = sql.split(" ", 4)[2].gsub('"', '')
473: 
474:         # Try an insert with 'returning id' if available (PG >= 8.2)
475:         if supports_insert_with_returning?
476:           pk, sequence_name = *pk_and_sequence_for(table) unless pk
477:           if pk
478:             id = select_value("#{sql} RETURNING #{quote_column_name(pk)}")
479:             clear_query_cache
480:             return id
481:           end
482:         end
483: 
484:         # Otherwise, insert then grab last_insert_id.
485:         if insert_id = super
486:           insert_id
487:         else
488:           # If neither pk nor sequence name is given, look them up.
489:           unless pk || sequence_name
490:             pk, sequence_name = *pk_and_sequence_for(table)
491:           end
492: 
493:           # If a pk is given, fallback to default sequence name.
494:           # Don't fetch last insert id for a table without a pk.
495:           if pk && sequence_name ||= default_sequence_name(table, pk)
496:             last_insert_id(table, sequence_name)
497:           end
498:         end
499:       end
outside_transaction?()

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

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 570
570:         def outside_transaction?
571:           @connection.transaction_status == PGconn::PQTRANS_IDLE
572:         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 vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 415
415:       def quote_table_name(name)
416:         schema, name_part = extract_pg_identifier_from_name(name.to_s)
417: 
418:         unless name_part
419:           quote_column_name(schema)
420:         else
421:           table_name, name_part = extract_pg_identifier_from_name(name_part)
422:           "#{quote_column_name(schema)}.#{quote_column_name(table_name)}"
423:         end
424:       end
reconnect!()

Close then reopen the connection.

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 228
228:       def reconnect!
229:         if @connection.respond_to?(:reset)
230:           @connection.reset
231:           configure_connection
232:         else
233:           disconnect!
234:           connect
235:         end
236:       end
release_savepoint()

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 583
583:       def release_savepoint
584:         execute("RELEASE SAVEPOINT #{current_savepoint_name}")
585:       end
remove_index(table_name, options = {})

Drops an index from a table.

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 882
882:       def remove_index(table_name, options = {})
883:         execute "DROP INDEX #{quote_table_name(index_name(table_name, options))}"
884:       end
rename_column(table_name, column_name, new_column_name)

Renames a column in a table.

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 877
877:       def rename_column(table_name, column_name, new_column_name)
878:         execute "ALTER TABLE #{quote_table_name(table_name)} RENAME COLUMN #{quote_column_name(column_name)} TO #{quote_column_name(new_column_name)}"
879:       end
rename_table(name, new_name)

Renames a table.

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 821
821:       def rename_table(name, new_name)
822:         execute "ALTER TABLE #{quote_table_name(name)} RENAME TO #{quote_table_name(new_name)}"
823:       end
rollback_db_transaction()

Aborts a transaction.

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 563
563:       def rollback_db_transaction
564:         execute "ROLLBACK"
565:       end
rollback_to_savepoint()

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 579
579:       def rollback_to_savepoint
580:         execute("ROLLBACK TO SAVEPOINT #{current_savepoint_name}")
581:       end
schema_search_path()

Returns the active schema search path.

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 728
728:       def schema_search_path
729:         @schema_search_path ||= query('SHOW search_path')[0][0]
730:       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 vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 720
720:       def schema_search_path=(schema_csv)
721:         if schema_csv
722:           execute "SET search_path TO #{schema_csv}"
723:           @schema_search_path = schema_csv
724:         end
725:       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 vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 465
465:       def select_rows(sql, name = nil)
466:         select_raw(sql, name).last
467:       end
supports_ddl_transactions?()

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 272
272:       def supports_ddl_transactions?
273:         true
274:       end
supports_insert_with_returning?()

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 268
268:       def supports_insert_with_returning?
269:         postgresql_version >= 80200
270:       end
supports_migrations?()

Does PostgreSQL support migrations?

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 248
248:       def supports_migrations?
249:         true
250:       end
supports_savepoints?()

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 276
276:       def supports_savepoints?
277:         true
278:       end
supports_standard_conforming_strings?()

Does PostgreSQL support standard conforming strings?

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 253
253:       def supports_standard_conforming_strings?
254:         # Temporarily set the client message level above error to prevent unintentional
255:         # error messages in the logs when working on a PostgreSQL database server that
256:         # does not support standard conforming strings.
257:         client_min_messages_old = client_min_messages
258:         self.client_min_messages = 'panic'
259: 
260:         # postgres-pr does not raise an exception when client_min_messages is set higher
261:         # than error and "SHOW standard_conforming_strings" fails, but returns an empty
262:         # PGresult instead.
263:         has_support = query('SHOW standard_conforming_strings')[0][0] rescue false
264:         self.client_min_messages = client_min_messages_old
265:         has_support
266:       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 vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 282
282:       def table_alias_length
283:         @table_alias_length ||= (postgresql_version >= 80000 ? query('SHOW max_identifier_length')[0][0].to_i : 63)
284:       end
tables(name = nil)

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

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 642
642:       def tables(name = nil)
643:         schemas = schema_search_path.split(/,/).map { |p| quote(p) }.join(',')
644:         query("SELECT tablename\nFROM pg_tables\nWHERE schemaname IN (\#{schemas})\n", name).map { |row| row[0] }
645:       end
type_to_sql(type, limit = nil, precision = nil, scale = nil)

Maps logical Rails types to PostgreSQL-specific data types.

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 887
887:       def type_to_sql(type, limit = nil, precision = nil, scale = nil)
888:         return super unless type.to_s == 'integer'
889: 
890:         case limit
891:           when 1..2;      'smallint'
892:           when 3..4, nil; 'integer'
893:           when 5..8;      'bigint'
894:           else raise(ActiveRecordError, "No integer type has byte size #{limit}. Use a numeric with precision 0 instead.")
895:         end
896:       end
unescape_bytea(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 vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 319
319:       def unescape_bytea(value)
320:         # In each case, check if the value actually is escaped PostgreSQL bytea output
321:         # or an unescaped Active Record attribute that was just written.
322:         if PGconn.respond_to?(:unescape_bytea)
323:           self.class.instance_eval do
324:             define_method(:unescape_bytea) do |value|
325:               if value =~ /\\\d{3}/
326:                 PGconn.unescape_bytea(value)
327:               else
328:                 value
329:               end
330:             end
331:           end
332:         else
333:           self.class.instance_eval do
334:             define_method(:unescape_bytea) do |value|
335:               if value =~ /\\\d{3}/
336:                 result = ''
337:                 i, max = 0, value.size
338:                 while i < max
339:                   char = value[i]
340:                   if char == ?\\
341:                     if value[i+1] == ?\\
342:                       char = ?\\
343:                       i += 1
344:                     else
345:                       char = value[i+1..i+3].oct
346:                       i += 3
347:                     end
348:                   end
349:                   result << char
350:                   i += 1
351:                 end
352:                 result
353:               else
354:                 value
355:               end
356:             end
357:           end
358:         end
359:         unescape_bytea(value)
360:       end
update_sql(sql, name = nil)

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

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 548
548:       def update_sql(sql, name = nil)
549:         super.cmd_tuples
550:       end
Protected Instance methods
postgresql_version()

Returns the version of the connected PostgreSQL version.

[ show source ]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 935
935:         def postgresql_version
936:           @postgresql_version ||=
937:             if @connection.respond_to?(:server_version)
938:               @connection.server_version
939:             else
940:               # Mimic PGconn.server_version behavior
941:               begin
942:                 query('SELECT version()')[0][0] =~ /PostgreSQL (\d+)\.(\d+)\.(\d+)/
943:                 ($1.to_i * 10000) + ($2.to_i * 100) + $3.to_i
944:               rescue
945:                 0
946:               end
947:             end
948:         end