Active Record PostgreSQL Adapter

The PostgreSQL adapter works with the native C (github.com/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 username.

  • :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"
DEADLOCK_DETECTED = "40P01"
DUPLICATE_DATABASE = "42P04"
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 }, bigint: { name: "bigint" }, float: { name: "float" }, decimal: { name: "decimal" }, datetime: {}, # set dynamically based on datetime_type timestamp: { name: "timestamp" }, timestamptz: { name: "timestamptz" }, 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" }, enum: {} # special type https://www.postgresql.org/docs/current/datatype-enum.html }
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
📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 115
      class_attribute :create_unlogged_tables, default: false
🔎 See on GitHub

datetime_type

PostgreSQL supports multiple types for DateTimes. By default, if you use datetime in migrations, Rails will translate this to a PostgreSQL “timestamp without time zone”. Change this in an initializer to use another NATIVE_DATABASE_TYPES. For example, to store DateTimes as “timestamp with time zone”:

ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.datetime_type = :timestamptz

Or if you are adding a custom type:

ActiveRecord::ConnectionAdapters::PostgreSQLAdapter::NATIVE_DATABASE_TYPES[:my_custom_type] = { name: "my_custom_type_name" }
ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.datetime_type = :my_custom_type

If you’re using :ruby as your config.active_record.schema_format and you change this setting, you should immediately run bin/rails db:migrate to update the types in your schema.rb.

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 133
      class_attribute :datetime_type, default: :timestamp
🔎 See on GitHub

dbconsole(config, options = {})

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 84
        def dbconsole(config, options = {})
          pg_config = config.configuration_hash

          ENV["PGUSER"]         = pg_config[:username] if pg_config[:username]
          ENV["PGHOST"]         = pg_config[:host] if pg_config[:host]
          ENV["PGPORT"]         = pg_config[:port].to_s if pg_config[:port]
          ENV["PGPASSWORD"]     = pg_config[:password].to_s if pg_config[:password] && options[:include_password]
          ENV["PGSSLMODE"]      = pg_config[:sslmode].to_s if pg_config[:sslmode]
          ENV["PGSSLCERT"]      = pg_config[:sslcert].to_s if pg_config[:sslcert]
          ENV["PGSSLKEY"]       = pg_config[:sslkey].to_s if pg_config[:sslkey]
          ENV["PGSSLROOTCERT"]  = pg_config[:sslrootcert].to_s if pg_config[:sslrootcert]
          if pg_config[:variables]
            ENV["PGOPTIONS"] = pg_config[:variables].filter_map do |name, value|
              "-c #{name}=#{value.to_s.gsub(/[ \\]/, '\\\\\0')}" unless value == ":default" || value == :default
            end.join(" ")
          end
          find_cmd_and_exec("psql", config.database)
        end
🔎 See on GitHub

new(...)

Initializes and connects a PostgreSQL adapter.

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 317
      def initialize(...)
        super

        conn_params = @config.compact

        # Map ActiveRecords param names to PGs.
        conn_params[:user] = conn_params.delete(:username) if conn_params[:username]
        conn_params[:dbname] = conn_params.delete(:database) if conn_params[:database]

        # Forward only valid config params to PG::Connection.connect.
        valid_conn_param_keys = PG::Connection.conndefaults_hash.keys + [:requiressl]
        conn_params.slice!(*valid_conn_param_keys)

        @connection_parameters = conn_params

        @max_identifier_length = nil
        @type_map = nil
        @raw_connection = nil
        @notice_receiver_sql_warnings = []

        @use_insert_returning = @config.key?(:insert_returning) ? self.class.type_cast_config_to_boolean(@config[:insert_returning]) : true
      end
🔎 See on GitHub

new_client(conn_params)

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 68
        def new_client(conn_params)
          PG.connect(**conn_params)
        rescue ::PG::Error => error
          if conn_params && conn_params[:dbname] == "postgres"
            raise ActiveRecord::ConnectionNotEstablished, error.message
          elsif conn_params && conn_params[:dbname] && error.message.include?(conn_params[:dbname])
            raise ActiveRecord::NoDatabaseError.db_error(conn_params[:dbname])
          elsif conn_params && conn_params[:user] && error.message.include?(conn_params[:user])
            raise ActiveRecord::DatabaseConnectionError.username_error(conn_params[:user])
          elsif conn_params && conn_params[:host] && error.message.include?(conn_params[:host])
            raise ActiveRecord::DatabaseConnectionError.hostname_error(conn_params[:host])
          else
            raise ActiveRecord::ConnectionNotEstablished, error.message
          end
        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 341
      def active?
        @lock.synchronize do
          return false unless @raw_connection
          @raw_connection.query ";"
        end
        true
      rescue PG::Error
        false
      end
🔎 See on GitHub

add_enum_value(type_name, value, options = {})

Add enum value to an existing enum type.

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 565
      def add_enum_value(type_name, value, options = {})
        before, after = options.values_at(:before, :after)
        sql = +"ALTER TYPE #{quote_table_name(type_name)} ADD VALUE '#{value}'"

        if before && after
          raise ArgumentError, "Cannot have both :before and :after at the same time"
        elsif before
          sql << " BEFORE '#{before}'"
        elsif after
          sql << " AFTER '#{after}'"
        end

        execute(sql).tap { reload_type_map }
      end
🔎 See on GitHub

create_enum(name, values, **options)

Given a name and an array of values, creates an enum type.

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 520
      def create_enum(name, values, **options)
        sql_values = values.map { |s| quote(s) }.join(", ")
        scope = quoted_scope(name)
        query = <<~SQL
          DO $$
          BEGIN
              IF NOT EXISTS (
                SELECT 1
                FROM pg_type t
                JOIN pg_namespace n ON t.typnamespace = n.oid
                WHERE t.typname = #{scope[:name]}
                  AND n.nspname = #{scope[:schema]}
              ) THEN
                  CREATE TYPE #{quote_table_name(name)} AS ENUM (#{sql_values});
              END IF;
          END
          $$;
        SQL
        internal_exec_query(query)
      end
🔎 See on GitHub

disable_extension(name, force: false)

Removes an extension from the database.

:force

Set to :cascade to drop dependent objects as well. Defaults to false.

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 478
      def disable_extension(name, force: false)
        internal_exec_query("DROP EXTENSION IF EXISTS \"#{name}\"#{' CASCADE' if force == :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 378
      def disconnect!
        @lock.synchronize do
          super
          @raw_connection&.close rescue nil
          @raw_connection = nil
        end
      end
🔎 See on GitHub

drop_enum(name, values = nil, **options)

Drops an enum type.

If the if_exists: true option is provided, the enum is dropped only if it exists. Otherwise, if the enum doesn’t exist, an error is raised.

The values parameter will be ignored if present. It can be helpful to provide this in a migration’s change method so it can be reverted. In that case, values will be used by create_enum.

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 550
      def drop_enum(name, values = nil, **options)
        query = <<~SQL
          DROP TYPE#{' IF EXISTS' if options[:if_exists]} #{quote_table_name(name)};
        SQL
        internal_exec_query(query)
      end
🔎 See on GitHub

enable_extension(name, **)

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 465
      def enable_extension(name, **)
        schema, name = name.to_s.split(".").values_at(-2, -1)
        sql = +"CREATE EXTENSION IF NOT EXISTS \"#{name}\""
        sql << " SCHEMA #{schema}" if schema

        internal_exec_query(sql).tap { reload_type_map }
      end
🔎 See on GitHub

enum_types()

Returns a list of defined enum types, and their values.

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 497
      def enum_types
        query = <<~SQL
          SELECT
            type.typname AS name,
            type.OID AS oid,
            n.nspname AS schema,
            string_agg(enum.enumlabel, ',' ORDER BY enum.enumsortorder) AS value
          FROM pg_enum AS enum
          JOIN pg_type AS type ON (type.oid = enum.enumtypid)
          JOIN pg_namespace n ON type.typnamespace = n.oid
          WHERE n.nspname = ANY (current_schemas(false))
          GROUP BY type.OID, n.nspname, type.typname;
        SQL

        internal_exec_query(query, "SCHEMA", allow_retry: true, materialize_transactions: false).cast_values.each_with_object({}) do |row, memo|
          name, schema = row[0], row[2]
          schema = nil if schema == current_schema
          full_name = [schema, name].compact.join(".")
          memo[full_name] = row.last
        end.to_a
      end
🔎 See on GitHub

extension_available?(name)

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 484
      def extension_available?(name)
        query_value("SELECT true FROM pg_available_extensions WHERE name = #{quote(name)}", "SCHEMA")
      end
🔎 See on GitHub

extension_enabled?(name)

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 488
      def extension_enabled?(name)
        query_value("SELECT installed_version IS NOT NULL FROM pg_available_extensions WHERE name = #{quote(name)}", "SCHEMA")
      end
🔎 See on GitHub

extensions()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 492
      def extensions
        internal_exec_query("SELECT extname FROM pg_extension", "SCHEMA", allow_retry: true, materialize_transactions: false).cast_values
      end
🔎 See on GitHub

index_algorithms()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 284
      def index_algorithms
        { concurrently: "CONCURRENTLY" }
      end
🔎 See on GitHub

max_identifier_length()

Returns the configured supported identifier length supported by PostgreSQL

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 595
      def max_identifier_length
        @max_identifier_length ||= query_value("SHOW max_identifier_length", "SCHEMA").to_i
      end
🔎 See on GitHub

rename_enum(name, options = {})

Rename an existing enum type to something else.

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 558
      def rename_enum(name, options = {})
        to = options.fetch(:to) { raise ArgumentError, ":to is required" }

        exec_query("ALTER TYPE #{quote_table_name(name)} RENAME TO #{to}").tap { reload_type_map }
      end
🔎 See on GitHub

rename_enum_value(type_name, options = {})

Rename enum value on an existing enum type.

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 581
      def rename_enum_value(type_name, options = {})
        unless database_version >= 10_00_00 # >= 10.0
          raise ArgumentError, "Renaming enum values is only supported in PostgreSQL 10 or later"
        end

        from = options.fetch(:from) { raise ArgumentError, ":from is required" }
        to = options.fetch(:to) { raise ArgumentError, ":to is required" }

        execute("ALTER TYPE #{quote_table_name(type_name)} RENAME VALUE '#{from}' TO '#{to}'").tap {
          reload_type_map
        }
      end
🔎 See on GitHub

reset!()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 363
      def reset!
        @lock.synchronize do
          return connect! unless @raw_connection

          unless @raw_connection.transaction_status == ::PG::PQTRANS_IDLE
            @raw_connection.query "ROLLBACK"
          end
          @raw_connection.query "DISCARD ALL"

          super
        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 608
      def session_auth=(user)
        clear_cache!
        internal_execute("SET SESSION AUTHORIZATION #{user}", nil, materialize_transactions: true)
      end
🔎 See on GitHub

set_standard_conforming_strings()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 404
      def set_standard_conforming_strings
        internal_execute("SET standard_conforming_strings = on")
      end
🔎 See on GitHub

supports_advisory_locks?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 412
      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 189
      def supports_bulk_alter?
        true
      end
🔎 See on GitHub

supports_check_constraints?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 221
      def supports_check_constraints?
        true
      end
🔎 See on GitHub

supports_comments?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 253
      def supports_comments?
        true
      end
🔎 See on GitHub

supports_common_table_expressions?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 443
      def supports_common_table_expressions?
        true
      end
🔎 See on GitHub

supports_datetime_with_precision?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 245
      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 408
      def supports_ddl_transactions?
        true
      end
🔎 See on GitHub

supports_deferrable_constraints?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 237
      def supports_deferrable_constraints?
        true
      end
🔎 See on GitHub

supports_exclusion_constraints?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 225
      def supports_exclusion_constraints?
        true
      end
🔎 See on GitHub

supports_explain?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 416
      def supports_explain?
        true
      end
🔎 See on GitHub

supports_expression_index?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 209
      def supports_expression_index?
        true
      end
🔎 See on GitHub

supports_extensions?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 420
      def supports_extensions?
        true
      end
🔎 See on GitHub

supports_foreign_keys?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 217
      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 428
      def supports_foreign_tables?
        true
      end
🔎 See on GitHub

supports_index_include?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 205
      def supports_index_include?
        database_version >= 11_00_00 # >= 11.0
      end
🔎 See on GitHub

supports_index_sort_order?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 193
      def supports_index_sort_order?
        true
      end
🔎 See on GitHub

supports_insert_conflict_target?()

Alias for: supports_insert_on_conflict?

supports_insert_on_conflict?()

Also aliased as: supports_insert_on_duplicate_skip?, supports_insert_on_duplicate_update?, supports_insert_conflict_target?
📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 269
      def supports_insert_on_conflict?
        database_version >= 9_05_00 # >= 9.5
      end
🔎 See on GitHub

supports_insert_on_duplicate_skip?()

Alias for: supports_insert_on_conflict?

supports_insert_on_duplicate_update?()

Alias for: supports_insert_on_conflict?

supports_insert_returning?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 265
      def supports_insert_returning?
        true
      end
🔎 See on GitHub

supports_json?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 249
      def supports_json?
        true
      end
🔎 See on GitHub

supports_lazy_transactions?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 447
      def supports_lazy_transactions?
        true
      end
🔎 See on GitHub

supports_materialized_views?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 424
      def supports_materialized_views?
        true
      end
🔎 See on GitHub

supports_nulls_not_distinct?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 280
      def supports_nulls_not_distinct?
        database_version >= 15_00_00 # >= 15.0
      end
🔎 See on GitHub

supports_optimizer_hints?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 436
      def supports_optimizer_hints?
        unless defined?(@has_pg_hint_plan)
          @has_pg_hint_plan = extension_available?("pg_hint_plan")
        end
        @has_pg_hint_plan
      end
🔎 See on GitHub

supports_partial_index?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 201
      def supports_partial_index?
        true
      end
🔎 See on GitHub

supports_partitioned_indexes?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 197
      def supports_partitioned_indexes?
        database_version >= 11_00_00 # >= 11.0
      end
🔎 See on GitHub

supports_pgcrypto_uuid?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 432
      def supports_pgcrypto_uuid?
        database_version >= 9_04_00 # >= 9.4
      end
🔎 See on GitHub

supports_restart_db_transaction?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 261
      def supports_restart_db_transaction?
        database_version >= 12_00_00 # >= 12.0
      end
🔎 See on GitHub

supports_savepoints?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 257
      def supports_savepoints?
        true
      end
🔎 See on GitHub

supports_transaction_isolation?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 213
      def supports_transaction_isolation?
        true
      end
🔎 See on GitHub

supports_unique_constraints?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 229
      def supports_unique_constraints?
        true
      end
🔎 See on GitHub

supports_validate_constraints?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 233
      def supports_validate_constraints?
        true
      end
🔎 See on GitHub

supports_views?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 241
      def supports_views?
        true
      end
🔎 See on GitHub

supports_virtual_columns?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 276
      def supports_virtual_columns?
        database_version >= 12_00_00 # >= 12.0
      end
🔎 See on GitHub

table_name_length()

Returns the maximum length of a table name.

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 600
      def table_name_length
        # PostgreSQL automatically creates an index for PRIMARY KEY with name consisting of
        # truncated table name and "_pkey" suffix fitting into max_identifier_length number of characters.
        # We allow smaller table names to be able to correctly rename this index when renaming the table.
        max_identifier_length - "_pkey".length
      end
🔎 See on GitHub

use_insert_returning?()

📝 Source code 
# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 613
      def use_insert_returning?
        @use_insert_returning
      end
🔎 See on GitHub