Advanced search: all group_contact records being retrieved but not used

I've found a case where Civi performs an unnecessary and expensive query. I have a fix.

To reproduce: With CiviCRM 2.2.0, invoke Advanced Search, using a profile in the Search View, and using criteria that do not include groups.

The problem: At line 591 in CRM/Contact/Selector.php, a call is made to CRM_Core_DAO::commonRetrieve() that results in the query "SELECT * FROM civicrm_group_contact" being made. On my server this leads to an "out-of-memory" error, which I could fix by raising limits, but I'd prefer to see fixed by removing the issue.

• The problem occurs when $result->status is empty, no group is selected in the search criteria, and there is no contact_id in $row. Under these conditions, all group_contacts are retrieved, and the first one is placed in $gcDefaults.
• Not only is the first one most probably the wrong one, but it's an unnecessary overhead to perform this query
• In my fix, I test whether the group_id and contact_id are both non-empty before making the call. Otherwise I set $row['status'] to a value which is non-empty and not equal to any of the valid values ('-' in my case).
• I suggest someone looks at the condition "if ( empty( $result->status ) )". It's not clear to me that this is a sufficient test. I didn't change that condition because I didn't understand the side-effects. But I expect that this is the condition which needs to be strengthened.