Merge pull request #23515 from kamipo/extract_arel_visitor

Extract `arel_visitor` and move up to the abstract adapter

activerecord/lib/active_record/connection_adapters/abstract_adapter.rb

@@ -104,9 +104,15 @@ def initialize(connection, logger = nil, config = {}) # :nodoc:
         @config              = config
         @pool                = nil
         @schema_cache        = SchemaCache.new self
-        @visitor             = nil
-        @prepared_statements = false
         @quoted_column_names, @quoted_table_names = {}, {}
+        @visitor             = arel_visitor
+
+        if self.class.type_cast_config_to_boolean(config.fetch(:prepared_statements) { true })
+          @prepared_statements = true
+          @visitor.extend(DetermineIfPreparableVisitor)
+        else
+          @prepared_statements = false
+        end
       end
 
       class Version
@@ -142,6 +148,10 @@ def collector
         end
       end
 
+      def arel_visitor # :nodoc:
+        (Arel::Visitors::VISITORS[@config[:adapter]] || Arel::Visitors::ToSql).new(self)
+      end
+
       def valid_type?(type)
         true
       end

activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb

@@ -55,15 +55,6 @@ def schema_creation
       def initialize(connection, logger, connection_options, config)
         super(connection, logger, config)
 
-        @visitor = Arel::Visitors::MySQL.new self
-
-        if self.class.type_cast_config_to_boolean(config.fetch(:prepared_statements) { true })
-          @prepared_statements = true
-          @visitor.extend(DetermineIfPreparableVisitor)
-        else
-          @prepared_statements = false
-        end
-
         if version < '5.0.0'
           raise "Your version of MySQL (#{full_version.match(/^\d+\.\d+\.\d+/)[0]}) is too old. Active Record supports MySQL >= 5.0."
         end

activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb

@@ -203,14 +203,6 @@ def connection_active?
       def initialize(connection, logger, connection_parameters, config)
         super(connection, logger, config)
 
-        @visitor = Arel::Visitors::PostgreSQL.new self
-        if self.class.type_cast_config_to_boolean(config.fetch(:prepared_statements) { true })
-          @prepared_statements = true
-          @visitor.extend(DetermineIfPreparableVisitor)
-        else
-          @prepared_statements = false
-        end
-
         @connection_parameters = connection_parameters
 
         # @local_tz is initialized as nil to avoid warnings when connect tries to use it

activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb

@@ -85,15 +85,6 @@ def initialize(connection, logger, connection_options, config)
 
         @active     = nil
         @statements = StatementPool.new(self.class.type_cast_config_to_integer(config.fetch(:statement_limit) { 1000 }))
-
-        @visitor = Arel::Visitors::SQLite.new self
-
-        if self.class.type_cast_config_to_boolean(config.fetch(:prepared_statements) { true })
-          @prepared_statements = true
-          @visitor.extend(DetermineIfPreparableVisitor)
-        else
-          @prepared_statements = false
-        end
       end
 
       def supports_ddl_transactions?