Unprepared Visitor + unprepared_statement

6 files changed, 33 insertions, 3 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 3b140b9ec3..73c6cd5a98 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,5 +1,17 @@
 ## Rails 4.0.0 (unreleased) ##
 
+*   Created block to by-pass the prepared statement bindings.
+    This will allow to compose fragments of large SQL statements to
+    avoid multiple round-trips between Ruby and the DB.
+
+    Example:
+
+        sql = Post.connection.unprepared_statement do
+            Post.first.comments.to_sql
+        end
+
+    *Cédric Fabianski*
+
 *   Expand `#cache_key` to consult all relevant updated timestamps.
 
     Previously only `updated_at` column was checked, now it will
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
index ff9de712bc..7949bcb5ce 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
@@ -118,6 +118,17 @@ module ActiveRecord
         @in_use = false
       end
 
+      def unprepared_visitor
+        self.class::BindSubstitution.new self
+      end
+
+      def unprepared_statement
+        old, @visitor = @visitor, unprepared_visitor
+        yield
+      ensure
+        @visitor = old
+      end
+
       # Returns the human-readable name of the adapter. Use mixed case - one
       # can always use downcase if needed.
       def adapter_name
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 be4a30aed9..f88f5742a8 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
@@ -143,7 +143,7 @@ module ActiveRecord
         if self.class.type_cast_config_to_boolean(config.fetch(:prepared_statements) { true })
           @visitor = Arel::Visitors::MySQL.new self
         else
-          @visitor = BindSubstitution.new self
+          @visitor = unprepared_visitor
         end
       end
 
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index c91e1b3fb9..691b2ab37f 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -489,7 +489,7 @@ module ActiveRecord
         if self.class.type_cast_config_to_boolean(config.fetch(:prepared_statements) { true })
           @visitor = Arel::Visitors::PostgreSQL.new self
         else
-          @visitor = BindSubstitution.new self
+          @visitor = unprepared_visitor
         end
 
         @connection_parameters, @config = connection_parameters, config
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
index 981c4c96a0..84fa1c7d5a 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
@@ -113,7 +113,7 @@ module ActiveRecord
         if self.class.type_cast_config_to_boolean(config.fetch(:prepared_statements) { true })
           @visitor = Arel::Visitors::SQLite.new self
         else
-          @visitor = BindSubstitution.new self
+          @visitor = unprepared_visitor
         end
       end
 
diff --git a/activerecord/test/cases/relations_test.rb b/activerecord/test/cases/relations_test.rb
index 8298d7534c..26cbb03892 100644
--- a/activerecord/test/cases/relations_test.rb
+++ b/activerecord/test/cases/relations_test.rb
@@ -714,6 +714,13 @@ class RelationTest < ActiveRecord::TestCase
     assert_equal [developers(:poor_jamis)], dev_with_count.to_a
   end
 
+  def test_relation_to_sql
+    sql = Post.connection.unprepared_statement do
+      Post.first.comments.to_sql
+    end
+    assert_no_match(/\?/, sql)
+  end
+
   def test_relation_merging_with_arel_equalities_keeps_last_equality
     devs = Developer.where(Developer.arel_table[:salary].eq(80000)).merge(
       Developer.where(Developer.arel_table[:salary].eq(9000))