Refactor `AbstractAdapter#initialize`

`pool` in args is unused anymore. And `config` is used in all adapters.

activerecord/lib/active_record/connection_adapters/abstract_adapter.rb

@@ -95,14 +95,15 @@ def self.type_cast_config_to_boolean(config)
 
       attr_reader :prepared_statements
 
-      def initialize(connection, logger = nil, pool = nil) #:nodoc:
+      def initialize(connection, logger = nil, config = {}) # :nodoc:
         super()
 
         @connection          = connection
         @owner               = nil
         @instrumenter        = ActiveSupport::Notifications.instrumenter
         @logger              = logger
-        @pool                = pool
+        @config              = config
+        @pool                = nil
         @schema_cache        = SchemaCache.new self
         @visitor             = nil
         @prepared_statements = false

activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb

@@ -143,8 +143,7 @@ def attributes_for_hash
 
       # FIXME: Make the first parameter more similar for the two adapters
       def initialize(connection, logger, connection_options, config)
-        super(connection, logger)
-        @config = config
+        super(connection, logger, config)
         @quoted_column_names, @quoted_table_names = {}, {}
 
         @visitor = Arel::Visitors::MySQL.new self

activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb

@@ -192,7 +192,7 @@ def connection_active?
 
       # Initializes and connects a PostgreSQL adapter.
       def initialize(connection, logger, connection_parameters, config)
-        super(connection, logger)
+        super(connection, logger, config)
 
         @visitor = Arel::Visitors::PostgreSQL.new self
         if self.class.type_cast_config_to_boolean(config.fetch(:prepared_statements) { true })
@@ -202,7 +202,7 @@ def initialize(connection, logger, connection_parameters, config)
           @prepared_statements = false
         end
 
-        @connection_parameters, @config = connection_parameters, config
+        @connection_parameters = connection_parameters
 
         # @local_tz is initialized as nil to avoid warnings when connect tries to use it
         @local_tz = nil

activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb

@@ -78,11 +78,10 @@ def schema_creation # :nodoc:
       end
 
       def initialize(connection, logger, connection_options, config)
-        super(connection, logger)
+        super(connection, logger, config)
 
         @active     = nil
         @statements = StatementPool.new(self.class.type_cast_config_to_integer(config.fetch(:statement_limit) { 1000 }))
-        @config = config
 
         @visitor = Arel::Visitors::SQLite.new self
         @quoted_column_names = {}