The PostgreSQL adapter works with the native C (bitbucket.org/ged/ruby-pg) driver.

Options:

  • :host - Defaults to a Unix-domain socket in /tmp. On machines without Unix-domain sockets, the default is to connect to localhost.

  • :port - Defaults to 5432.

  • :username - Defaults to be the same as the operating system name of the user running the application.

  • :password - Password to be used if the server demands password authentication.

  • :database - Defaults to be the same as the user name.

  • :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.

  • :variables - An optional hash of additional parameters that will be used in SET SESSION key = val calls on the connection.

  • :insert_returning - An optional boolean to control the use of RETURNING for INSERT statements defaults to true.

Any further options are used as connection parameters to libpq. See www.postgresql.org/docs/current/static/libpq-connect.html for the list of parameters.

In addition, default connection parameters of libpq can be set per environment variables. See www.postgresql.org/docs/current/static/libpq-envars.html .

Methods

Included Modules

Constants

ADAPTER_NAME = "PostgreSQL".freeze
CACHED_PLAN_HEURISTIC = "cached plan must not change result type".freeze
 

Annoyingly, the code for prepared statements whose return value may have changed is FEATURE_NOT_SUPPORTED.

This covers various different error types so we need to do additional work to classify the exception definitively as a ActiveRecord::PreparedStatementCacheExpired

Check here for more details: git.postgresql.org/gitweb/?p=postgresql.git;a=blob;f=src/backend/utils/cache/plancache.c#l573
DEADLOCK_DETECTED = "40P01"
FOREIGN_KEY_VIOLATION = "23503"
LOCK_NOT_AVAILABLE = "55P03"
NATIVE_DATABASE_TYPES = { primary_key: "bigserial primary key", string: { name: "character varying" }, text: { name: "text" }, integer: { name: "integer", limit: 4 }, float: { name: "float" }, decimal: { name: "decimal" }, datetime: { name: "timestamp" }, time: { name: "time" }, date: { name: "date" }, daterange: { name: "daterange" }, numrange: { name: "numrange" }, tsrange: { name: "tsrange" }, tstzrange: { name: "tstzrange" }, int4range: { name: "int4range" }, int8range: { name: "int8range" }, binary: { name: "bytea" }, boolean: { name: "boolean" }, xml: { name: "xml" }, tsvector: { name: "tsvector" }, hstore: { name: "hstore" }, inet: { name: "inet" }, cidr: { name: "cidr" }, macaddr: { name: "macaddr" }, uuid: { name: "uuid" }, json: { name: "json" }, jsonb: { name: "jsonb" }, ltree: { name: "ltree" }, citext: { name: "citext" }, point: { name: "point" }, line: { name: "line" }, lseg: { name: "lseg" }, box: { name: "box" }, path: { name: "path" }, polygon: { name: "polygon" }, circle: { name: "circle" }, bit: { name: "bit" }, bit_varying: { name: "bit varying" }, money: { name: "money" }, interval: { name: "interval" }, oid: { name: "oid" }, }
NOT_NULL_VIOLATION = "23502"
NUMERIC_VALUE_OUT_OF_RANGE = "22003"
QUERY_CANCELED = "57014"
SERIALIZATION_FAILURE = "40001"
UNIQUE_VIOLATION = "23505"
VALUE_LIMIT_VIOLATION = "22001"
 

See www.postgresql.org/docs/current/static/errcodes-appendix.html

Class Public methods

new(connection, logger, connection_parameters, config)

Initializes and connects a PostgreSQL adapter.

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 214
      def initialize(connection, logger, connection_parameters, config)
        super(connection, logger, config)

        @connection_parameters = connection_parameters

        # @local_tz is initialized as nil to avoid warnings when connect tries to use it
        @local_tz = nil
        @max_identifier_length = nil

        connect
        add_pg_encoders
        @statements = StatementPool.new @connection,
                                        self.class.type_cast_config_to_integer(config[:statement_limit])

        if postgresql_version < 90100
          raise "Your version of PostgreSQL (#{postgresql_version}) is too old. Active Record supports PostgreSQL >= 9.1."
        end

        add_pg_decoders

        @type_map = Type::HashLookupTypeMap.new
        initialize_type_map
        @local_tz = execute("SHOW TIME ZONE", "SCHEMA").first["TimeZone"]
        @use_insert_returning = @config.key?(:insert_returning) ? self.class.type_cast_config_to_boolean(@config[:insert_returning]) : true
      end
🔎 See on GitHub

Instance Public methods

active?()

Is this connection alive and ready for queries?

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 252
      def active?
        @lock.synchronize do
          @connection.query "SELECT 1"
        end
        true
      rescue PG::Error
        false
      end
🔎 See on GitHub

clear_cache!()

Clears the prepared statements cache.

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 241
      def clear_cache!
        @lock.synchronize do
          @statements.clear
        end
      end
🔎 See on GitHub

disable_extension(name)

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 357
      def disable_extension(name)
        exec_query("DROP EXTENSION IF EXISTS \"#{name}\" CASCADE").tap {
          reload_type_map
        }
      end
🔎 See on GitHub

disconnect!()

Disconnects from the database if already connected. Otherwise, this method does nothing.

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 284
      def disconnect!
        @lock.synchronize do
          super
          @connection.close rescue nil
        end
      end
🔎 See on GitHub

enable_extension(name)

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 351
      def enable_extension(name)
        exec_query("CREATE EXTENSION IF NOT EXISTS \"#{name}\"").tap {
          reload_type_map
        }
      end
🔎 See on GitHub

extension_enabled?(name)

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 363
      def extension_enabled?(name)
        res = exec_query("SELECT EXISTS(SELECT * FROM pg_available_extensions WHERE name = '#{name}' AND installed_version IS NOT NULL) as enabled", "SCHEMA")
        res.cast_values.first
      end
🔎 See on GitHub

extensions()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 368
      def extensions
        exec_query("SELECT extname FROM pg_extension", "SCHEMA").cast_values
      end
🔎 See on GitHub

index_algorithms()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 181
      def index_algorithms
        { concurrently: "CONCURRENTLY" }
      end
🔎 See on GitHub

index_name_length()

Alias for: max_identifier_length

max_identifier_length()

Returns the configured supported identifier length supported by PostgreSQL

Also aliased as: table_alias_length, index_name_length
📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 373
      def max_identifier_length
        @max_identifier_length ||= query_value("SHOW max_identifier_length", "SCHEMA").to_i
      end
🔎 See on GitHub

postgresql_version()

Returns the version of the connected PostgreSQL server.

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 400
      def postgresql_version
        @connection.server_version
      end
🔎 See on GitHub

reconnect!()

Close then reopen the connection.

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 262
      def reconnect!
        @lock.synchronize do
          super
          @connection.reset
          configure_connection
        end
      end
🔎 See on GitHub

reset!()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 270
      def reset!
        @lock.synchronize do
          clear_cache!
          reset_transaction
          unless @connection.transaction_status == ::PG::PQTRANS_IDLE
            @connection.query "ROLLBACK"
          end
          @connection.query "DISCARD ALL"
          configure_connection
        end
      end
🔎 See on GitHub

session_auth=(user)

Set the authorized user for this session

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 380
      def session_auth=(user)
        clear_cache!
        execute("SET SESSION AUTHORIZATION #{user}")
      end
🔎 See on GitHub

set_standard_conforming_strings()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 300
      def set_standard_conforming_strings
        execute("SET standard_conforming_strings = on", "SCHEMA")
      end
🔎 See on GitHub

supports_advisory_locks?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 308
      def supports_advisory_locks?
        true
      end
🔎 See on GitHub

supports_bulk_alter?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 133
      def supports_bulk_alter?
        true
      end
🔎 See on GitHub

supports_comments?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 173
      def supports_comments?
        true
      end
🔎 See on GitHub

supports_datetime_with_precision?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 165
      def supports_datetime_with_precision?
        true
      end
🔎 See on GitHub

supports_ddl_transactions?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 304
      def supports_ddl_transactions?
        true
      end
🔎 See on GitHub

supports_explain?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 312
      def supports_explain?
        true
      end
🔎 See on GitHub

supports_expression_index?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 145
      def supports_expression_index?
        true
      end
🔎 See on GitHub

supports_extensions?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 316
      def supports_extensions?
        true
      end
🔎 See on GitHub

supports_foreign_keys?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 153
      def supports_foreign_keys?
        true
      end
🔎 See on GitHub

supports_foreign_tables?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 329
      def supports_foreign_tables?
        postgresql_version >= 90300
      end
🔎 See on GitHub

supports_index_sort_order?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 137
      def supports_index_sort_order?
        true
      end
🔎 See on GitHub

supports_json?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 169
      def supports_json?
        postgresql_version >= 90200
      end
🔎 See on GitHub

supports_materialized_views?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 325
      def supports_materialized_views?
        postgresql_version >= 90300
      end
🔎 See on GitHub

supports_partial_index?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 141
      def supports_partial_index?
        true
      end
🔎 See on GitHub

supports_pgcrypto_uuid?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 333
      def supports_pgcrypto_uuid?
        postgresql_version >= 90400
      end
🔎 See on GitHub

supports_ranges?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 320
      def supports_ranges?
        # Range datatypes weren't introduced until PostgreSQL 9.2
        postgresql_version >= 90200
      end
🔎 See on GitHub

supports_savepoints?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 177
      def supports_savepoints?
        true
      end
🔎 See on GitHub

supports_transaction_isolation?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 149
      def supports_transaction_isolation?
        true
      end
🔎 See on GitHub

supports_validate_constraints?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 157
      def supports_validate_constraints?
        true
      end
🔎 See on GitHub

supports_views?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 161
      def supports_views?
        true
      end
🔎 See on GitHub

table_alias_length()

Alias for: max_identifier_length

truncate(table_name, name = nil)

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 247
      def truncate(table_name, name = nil)
        exec_query "TRUNCATE TABLE #{quote_table_name(table_name)}", name, []
      end
🔎 See on GitHub

use_insert_returning?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 385
      def use_insert_returning?
        @use_insert_returning
      end
🔎 See on GitHub