fix(query): move the bitmap when drop first rows.

source/common/src/tdatablock.c

@@ -1278,12 +1278,11 @@ static void doShiftBitmap(char* nullBitmap, size_t n, size_t total) {
   } else {
     int32_t tail = n % 8;
     int32_t  i = 0;
-
     uint8_t* p = (uint8_t*)nullBitmap;
-    while (i < len) {
-      uint8_t v = p[i];
 
-      p[i] = 0;
+    if (n < 8) {
+      while (i < len) {
+        uint8_t v = p[i];  // source bitmap value
         p[i] = (v << tail);
 
         if (i < len - 1) {
@@ -1293,9 +1292,24 @@ static void doShiftBitmap(char* nullBitmap, size_t n, size_t total) {
 
         i += 1;
       }
+    } else if (n > 8) {
+      int32_t gap = len - newLen;
+      while(i < newLen) {
+        uint8_t v = p[i + gap];
+        p[i] = (v << tail);
+
+        if (i < newLen - 1) {
+          uint8_t next = p[i + gap + 1];
+          p[i] |= (next >> (8 - tail));
+        }
+
+        i += 1;
+      }
+    }
   }
 }
 
+
 static void colDataTrimFirstNRows(SColumnInfoData* pColInfoData, size_t n, size_t total) {
   if (IS_VAR_DATA_TYPE(pColInfoData->info.type)) {
     memmove(pColInfoData->varmeta.offset, &pColInfoData->varmeta.offset[n], (total - n) * sizeof(int32_t));