diff --git a/src/resultset_merge.c b/src/resultset_merge.c
index 3d681b6..f7b56dd 100644
--- a/src/resultset_merge.c
+++ b/src/resultset_merge.c
@@ -1846,9 +1846,8 @@ heap_adjust(heap_type *heap, int s, int m, int *compare_failed)
                 j++;
             } else if (!heap->element[j + 1]->is_over) {
                 if (!heap->element[j]->refreshed && !heap->element[j + 1]->refreshed) {
-                    if (!heap->element[j]->is_prior_to) {
+                    if (heap->element[j]->is_prior_to == -1) {
                         j++;
-                    } else {
                     }
                 } else {
                     is_dup = 0;
@@ -1857,7 +1856,7 @@ heap_adjust(heap_type *heap, int s, int m, int *compare_failed)
                                      heap->element[j + 1]->record->data, &(heap->order_para),
                                      heap->element[j]->index, heap->element[j + 1]->index, &is_dup, compare_failed)) {
                         j++;
-                        heap->element[j]->is_prior_to = 0;
+                        heap->element[j]->is_prior_to = -1;
 
                     } else {
                         if (is_dup) {
diff --git a/src/resultset_merge.h b/src/resultset_merge.h
index 351b13d..a9ca531 100644
--- a/src/resultset_merge.h
+++ b/src/resultset_merge.h
@@ -54,11 +54,11 @@ typedef struct ORDER_BY {
 typedef struct {
     GList *record;
     int index;
+    int is_prior_to;
     unsigned int is_over:1;
     unsigned int is_err:1;
     unsigned int refreshed:1;
     unsigned int is_dup:1;
-    unsigned int is_prior_to:1;
 } heap_element;
 
 typedef struct order_by_para_s {