Ticket #15256: 15256.diff

wp-includes/query.php

@@ -1730 +1730 @@
                                 $in = ($cat > 0);
                                 $cat = abs($cat);
                                 if ( $in ) {
-                                        $q['category__in'][] = $cat;
-                                        $q['category__in'] = array_merge( $q['category__in'], get_term_children($cat, 'category') );
+                                        $q['category__in'][] = $cat; // children are included by default in get_tax_sql()
                                 } else {
                                         $q['category__not_in'][] = $cat;
                                         $q['category__not_in'] = array_merge( $q['category__not_in'], get_term_children($cat, 'category') );
@@ -1746 +1745 @@
                                 'taxonomy' => 'category',
                                 'terms' => $q['category__in'],
                                 'field' => 'term_id',
-                                'include_children' => false
                         );
                 }