From 8200b3ba325be07ebd579c57c7104434b0bf036e Mon Sep 17 00:00:00 2001
From: Ryuta Kamizono <kamipo@gmail.com>
Date: Sat, 6 Feb 2016 15:25:36 +0900
Subject: Extract `arel_visitor` and move up to the abstract adapter

---
 .../active_record/connection_adapters/abstract_adapter.rb  | 14 ++++++++++++--
 .../connection_adapters/abstract_mysql_adapter.rb          |  9 ---------
 .../connection_adapters/postgresql_adapter.rb              |  8 --------
 .../active_record/connection_adapters/sqlite3_adapter.rb   |  9 ---------
 4 files changed, 12 insertions(+), 28 deletions(-)

diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
index 069346253a..41e40494e6 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
@@ -104,9 +104,15 @@ module ActiveRecord
         @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 @@ module ActiveRecord
         end
       end
 
+      def arel_visitor # :nodoc:
+        (Arel::Visitors::VISITORS[@config[:adapter]] || Arel::Visitors::ToSql).new(self)
+      end
+
       def valid_type?(type)
         true
       end
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
index 8015d1ed9e..9cdbbc2467 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
@@ -57,15 +57,6 @@ module ActiveRecord
       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
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index 6497b1cc31..323f670d12 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -195,14 +195,6 @@ module ActiveRecord
       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
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
index 5c8e428bef..7adcbc9b64 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
@@ -85,15 +85,6 @@ module ActiveRecord
 
         @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?
-- 
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