ZF2 ResultSet和计数性能

Question

I'm using TableGateway with an attached custom RowGateway object. If I want to use the object returned by TableGateway->getSql()->select() to get a record count, the attached RowGateway object complains about a missing primary key in the result set.

   $tablegateway = new TableGateway('table', $adapter, new RowGatewayFeature(new AuditingRowGateway($primkey, 'table', $adapter), new ResultSet());
   $select = $tablegateway->getSql()->select();
   $select->columns(array('num' => new \Zend\Db\Sql\Expression('COUNT(*)')));
   $row = $tablegateway->selectWith($select)->current();

Result: Zend\Db\RowGateway\Exception\RuntimeException: While processing primary key data, a known key xxx was not found in the data array

I could work it around by issuing a normal (i.e. non-count) select:

$result = $tablegateway->selectWith($select);
$count = $result->count();

But not sure about this performance-wise compared to a 'SELECT COUNT(*)'.

Answer 1

Even though you want just a count value, if include the primary key in the columns array, it should work.

$select->columns(array($primkey, 'num' => new \Zend\Db\Sql\Expression('COUNT(*)')));