add a truncate method to the connection

it doesn't work on SQLite3 since it doesn't support truncate, but that's
OK.  If you call truncate on the connection, you're now bound to that
database (same as if you use hstore or any other db specific feature).

6 files changed, 38 insertions, 0 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index c02de2e979..ae4aac128e 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,5 @@
+*   Add a truncate method to the connection.
+
 *   Don't autosave unchanged has_one through records.
 
     *Alan Kennedy*, *Steve Parrington*
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb b/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb
index 98e96099cb..ff8b3e9890 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb
@@ -83,6 +83,11 @@ module ActiveRecord
         exec_query(sql, name, binds)
       end
 
+      # Executes the truncate statement.
+      def truncate(table_name, name = nil)
+        raise NotImplementedError
+      end
+
       # Executes update +sql+ statement in the context of this connection using
       # +binds+ as the bind substitutes. +name+ is logged along with
       # the executed +sql+ statement.
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 037fb69dfb..e4cfe843a8 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
@@ -389,6 +389,10 @@ module ActiveRecord
         end
       end
 
+      def truncate(table_name, name = nil)
+        execute "TRUNCATE TABLE #{quote_table_name(table_name)}", name
+      end
+
       def table_exists?(name)
         return false unless name.present?
         return true if tables(nil, nil, name).any?
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index 80461f3910..0d74cb6707 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -255,6 +255,10 @@ module ActiveRecord
         @statements.clear
       end
 
+      def truncate(table_name, name = nil)
+        exec_query "TRUNCATE TABLE #{quote_table_name(table_name)}", name, []
+      end
+
       # Is this connection alive and ready for queries?
       def active?
         @connection.query 'SELECT 1'
diff --git a/activerecord/test/cases/adapters/mysql2/connection_test.rb b/activerecord/test/cases/adapters/mysql2/connection_test.rb
index 0b2f59b0eb..62c5abbf41 100644
--- a/activerecord/test/cases/adapters/mysql2/connection_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/connection_test.rb
@@ -4,6 +4,8 @@ require 'support/connection_helper'
 class MysqlConnectionTest < ActiveRecord::TestCase
   include ConnectionHelper
 
+  fixtures :comments
+
   def setup
     super
     @subscriber = SQLSubscriber.new
@@ -24,6 +26,17 @@ class MysqlConnectionTest < ActiveRecord::TestCase
     end
   end
 
+  def test_truncate
+    rows = ActiveRecord::Base.connection.exec_query("select count(*) from comments")
+    count = rows.first.values.first
+    assert_operator count, :>, 0
+
+    ActiveRecord::Base.connection.truncate("comments")
+    rows = ActiveRecord::Base.connection.exec_query("select count(*) from comments")
+    count = rows.first.values.first
+    assert_equal 0, count
+  end
+
   def test_no_automatic_reconnection_after_timeout
     assert @connection.active?
     @connection.update('set @@wait_timeout=1')
diff --git a/activerecord/test/cases/adapters/postgresql/connection_test.rb b/activerecord/test/cases/adapters/postgresql/connection_test.rb
index d26cda46fa..7d179944d4 100644
--- a/activerecord/test/cases/adapters/postgresql/connection_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/connection_test.rb
@@ -8,6 +8,8 @@ module ActiveRecord
     class NonExistentTable < ActiveRecord::Base
     end
 
+    fixtures :comments
+
     def setup
       super
       @subscriber = SQLSubscriber.new
@@ -20,6 +22,14 @@ module ActiveRecord
       super
     end
 
+    def test_truncate
+      count = ActiveRecord::Base.connection.execute("select count(*) from comments").first['count'].to_i
+      assert_operator count, :>, 0
+      ActiveRecord::Base.connection.truncate("comments")
+      count = ActiveRecord::Base.connection.execute("select count(*) from comments").first['count'].to_i
+      assert_equal 0, count
+    end
+
     def test_encoding
       assert_not_nil @connection.encoding
     end