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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 .

Namespace
Methods
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Included Modules
Constants
ADAPTER_NAME = "PostgreSQL".freeze
 
NATIVE_DATABASE_TYPES = { primary_key: "serial primary key", string: { name: "character varying" }, text: { name: "text" }, integer: { name: "integer" }, 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" }, }
 
OID = PostgreSQL::OID #:nodoc:
 
OPERATION_ALIASES = { # :nodoc: "maximum" => "max", "minimum" => "min", "average" => "avg", }
 
VALUE_LIMIT_VIOLATION = "22001"
 

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

FOREIGN_KEY_VIOLATION = "23503"
 
UNIQUE_VIOLATION = "23505"
 
SERIALIZATION_FAILURE = "40001"
 
DEADLOCK_DETECTED = "40P01"
 
FEATURE_NOT_SUPPORTED = "0A000"
 
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

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

Initializes and connects a PostgreSQL adapter.

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 208
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
  @table_alias_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(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
Instance Public methods
active?()

Is this connection alive and ready for queries?

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 244
def active?
  @connection.query "SELECT 1"
  true
rescue PGError
  false
end
clear_cache!()

Clears the prepared statements cache.

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 235
def clear_cache!
  @statements.clear
end
disable_extension(name)
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 338
def disable_extension(name)
  exec_query("DROP EXTENSION IF EXISTS \"#{name}\" CASCADE").tap {
    reload_type_map
  }
end
disconnect!()

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

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 270
def disconnect!
  super
  @connection.close rescue nil
end
enable_extension(name)
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 332
def enable_extension(name)
  exec_query("CREATE EXTENSION IF NOT EXISTS \"#{name}\"").tap {
    reload_type_map
  }
end
extension_enabled?(name)
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 344
def extension_enabled?(name)
  if supports_extensions?
    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
end
extensions()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 352
def extensions
  if supports_extensions?
    exec_query("SELECT extname from pg_extension", "SCHEMA").cast_values
  else
    super
  end
end
index_algorithms()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 175
def index_algorithms
  { concurrently: "CONCURRENTLY" }
end
postgresql_version()

Returns the version of the connected PostgreSQL server.

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 399
def postgresql_version
  @connection.server_version
end
reconnect!()

Close then reopen the connection.

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 252
def reconnect!
  super
  @connection.reset
  configure_connection
end
reset!()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 258
def reset!
  clear_cache!
  reset_transaction
  unless @connection.transaction_status == ::PG::PQTRANS_IDLE
    @connection.query "ROLLBACK"
  end
  @connection.query "DISCARD ALL"
  configure_connection
end
session_auth=(user)

Set the authorized user for this session

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 366
def session_auth=(user)
  clear_cache!
  exec_query "SET SESSION AUTHORIZATION #{user}"
end
set_standard_conforming_strings()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 289
def set_standard_conforming_strings
  execute("SET standard_conforming_strings = on", "SCHEMA")
end
supports_advisory_locks?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 297
def supports_advisory_locks?
  true
end
supports_comments?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 167
def supports_comments?
  true
end
supports_datetime_with_precision?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 159
def supports_datetime_with_precision?
  true
end
supports_ddl_transactions?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 293
def supports_ddl_transactions?
  true
end
supports_explain?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 301
def supports_explain?
  true
end
supports_expression_index?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 143
def supports_expression_index?
  true
end
supports_extensions?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 305
def supports_extensions?
  true
end
supports_foreign_keys?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 151
def supports_foreign_keys?
  true
end
supports_index_sort_order?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 135
def supports_index_sort_order?
  true
end
supports_json?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 163
def supports_json?
  postgresql_version >= 90200
end
supports_materialized_views?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 314
def supports_materialized_views?
  postgresql_version >= 90300
end
supports_migrations?()

Returns true, since this connection adapter supports migrations.

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 280
def supports_migrations?
  true
end
supports_partial_index?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 139
def supports_partial_index?
  true
end
supports_ranges?()

Range datatypes weren't introduced until PostgreSQL 9.2

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 310
def supports_ranges?
  postgresql_version >= 90200
end
supports_savepoints?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 171
def supports_savepoints?
  true
end
supports_statement_cache?()

Returns true, since this connection adapter supports prepared statement caching.

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 131
def supports_statement_cache?
  true
end
supports_transaction_isolation?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 147
def supports_transaction_isolation?
  true
end
supports_views?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 155
def supports_views?
  true
end
table_alias_length()

Returns the configured supported identifier length supported by PostgreSQL

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 361
def table_alias_length
  @table_alias_length ||= query("SHOW max_identifier_length", "SCHEMA")[0][0].to_i
end
truncate(table_name, name = nil)
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 239
def truncate(table_name, name = nil)
  exec_query "TRUNCATE TABLE #{quote_table_name(table_name)}", name, []
end
use_insert_returning?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 371
def use_insert_returning?
  @use_insert_returning
end
valid_type?(type)
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 375
def valid_type?(type)
  !native_database_types[type].nil?
end
Instance Protected methods
translate_exception(exception, message)
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 412
def translate_exception(exception, message)
  return exception unless exception.respond_to?(:result)

  case exception.result.try(:error_field, PGresult::PG_DIAG_SQLSTATE)
  when UNIQUE_VIOLATION
    RecordNotUnique.new(message)
  when FOREIGN_KEY_VIOLATION
    InvalidForeignKey.new(message)
  when VALUE_LIMIT_VIOLATION
    ValueTooLong.new(message)
  when SERIALIZATION_FAILURE
    SerializationFailure.new(message)
  when DEADLOCK_DETECTED
    Deadlocked.new(message)
  else
    super
  end
end