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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 .

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Included Modules
Constants
ADAPTER_NAME = "PostgreSQL"
 
CACHED_PLAN_HEURISTIC = "cached plan must not change result type"
 

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
create_unlogged_tables

PostgreSQL allows the creation of “unlogged” tables, which do not record data in the PostgreSQL Write-Ahead Log. This can make the tables faster, but significantly increases the risk of data loss if the database crashes. As a result, this should not be used in production environments. If you would like all created tables to be unlogged in the test environment you can add the following line to your test.rb file:

ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.create_unlogged_tables = true
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 99
class_attribute :create_unlogged_tables, default: false
new(connection, logger, connection_parameters, config)

Initializes and connects a PostgreSQL adapter.

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 232
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

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

  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
Instance Public methods
active?()

Is this connection alive and ready for queries?

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 266
def active?
  @lock.synchronize do
    @connection.query "SELECT 1"
  end
  true
rescue PG::Error
  false
end
clear_cache!()

Clears the prepared statements cache.

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 255
def clear_cache!
  @lock.synchronize do
    @statements.clear
  end
end
disable_extension(name)
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 375
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 298
def disconnect!
  @lock.synchronize do
    super
    @connection.close rescue nil
  end
end
enable_extension(name)
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 369
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 381
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
extensions()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 386
def extensions
  exec_query("SELECT extname FROM pg_extension", "SCHEMA").cast_values
end
index_algorithms()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 199
def index_algorithms
  { concurrently: "CONCURRENTLY" }
end
index_name_length()
max_identifier_length()

Returns the configured supported identifier length supported by PostgreSQL

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 391
def max_identifier_length
  @max_identifier_length ||= query_value("SHOW max_identifier_length", "SCHEMA").to_i
end
postgresql_version()

Returns the version of the connected PostgreSQL server.

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 418
def postgresql_version
  @connection.server_version
end
reconnect!()

Close then reopen the connection.

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 276
def reconnect!
  @lock.synchronize do
    super
    @connection.reset
    configure_connection
  end
end
reset!()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 284
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
session_auth=(user)

Set the authorized user for this session

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 398
def session_auth=(user)
  clear_cache!
  execute("SET SESSION AUTHORIZATION #{user}")
end
set_standard_conforming_strings()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 314
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 322
def supports_advisory_locks?
  true
end
supports_bulk_alter?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 151
def supports_bulk_alter?
  true
end
supports_comments?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 191
def supports_comments?
  true
end
supports_datetime_with_precision?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 183
def supports_datetime_with_precision?
  true
end
supports_ddl_transactions?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 318
def supports_ddl_transactions?
  true
end
supports_explain?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 326
def supports_explain?
  true
end
supports_expression_index?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 163
def supports_expression_index?
  true
end
supports_extensions?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 330
def supports_extensions?
  true
end
supports_foreign_keys?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 171
def supports_foreign_keys?
  true
end
supports_foreign_tables?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 343
def supports_foreign_tables?
  postgresql_version >= 90300
end
supports_index_sort_order?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 155
def supports_index_sort_order?
  true
end
supports_json?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 187
def supports_json?
  postgresql_version >= 90200
end
supports_lazy_transactions?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 351
def supports_lazy_transactions?
  true
end
supports_materialized_views?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 339
def supports_materialized_views?
  postgresql_version >= 90300
end
supports_partial_index?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 159
def supports_partial_index?
  true
end
supports_pgcrypto_uuid?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 347
def supports_pgcrypto_uuid?
  postgresql_version >= 90400
end
supports_ranges?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 334
def supports_ranges?
  # Range datatypes weren't introduced until PostgreSQL 9.2
  postgresql_version >= 90200
end
supports_savepoints?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 195
def supports_savepoints?
  true
end
supports_transaction_isolation?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 167
def supports_transaction_isolation?
  true
end
supports_validate_constraints?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 175
def supports_validate_constraints?
  true
end
supports_views?()
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 179
def supports_views?
  true
end
table_alias_length()
truncate(table_name, name = nil)
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 261
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 403
def use_insert_returning?
  @use_insert_returning
end