Ticket #16812: query.patch

query.php

@@ -2211 +2211 @@
                         }
                 }
 
-                if ( !empty( $this->tax_query->queries ) || !empty( $q['meta_key'] ) ) {
+                if ( ( !empty( $this->tax_query->queries ) && !empty( $join ) ) || !empty( $q['meta_key'] ) ) {
                         $groupby = "{$wpdb->posts}.ID";
                 }