fix(query): check for null ptr before extract sort execution information.

source/libs/executor/src/sortoperator.c

@@ -732,12 +732,13 @@ void destroyMultiwayMergeOperatorInfo(void* param) {
 
 int32_t getMultiwayMergeExplainExecInfo(SOperatorInfo* pOptr, void** pOptrExplain, uint32_t* len) {
   ASSERT(pOptr != NULL);
-  SSortExecInfo* pInfo = taosMemoryCalloc(1, sizeof(SSortExecInfo));
+  SSortExecInfo* pSortExecInfo = taosMemoryCalloc(1, sizeof(SSortExecInfo));
 
-  SMultiwayMergeOperatorInfo* pOperatorInfo = (SMultiwayMergeOperatorInfo*)pOptr->info;
+  SMultiwayMergeOperatorInfo* pInfo = (SMultiwayMergeOperatorInfo*)pOptr->info;
+
+  *pSortExecInfo = tsortGetSortExecInfo(pInfo->pSortHandle);
+  *pOptrExplain = pSortExecInfo;
 
-  *pInfo = tsortGetSortExecInfo(pOperatorInfo->pSortHandle);
-  *pOptrExplain = pInfo;
   *len = sizeof(SSortExecInfo);
   return TSDB_CODE_SUCCESS;
 }

source/libs/executor/src/tsort.c

@@ -831,6 +831,10 @@ uint64_t tsortGetGroupId(STupleHandle* pVHandle) { return pVHandle->pBlock->info
 SSortExecInfo tsortGetSortExecInfo(SSortHandle* pHandle) {
   SSortExecInfo info = {0};
 
+  if (pHandle == NULL) {
+    info.sortMethod = SORT_QSORT_T; // by default
+    info.sortBuffer = 2 * 1048576;  // 2mb by default
+  } else {
     info.sortBuffer = pHandle->pageSize * pHandle->numOfPages;
     info.sortMethod = pHandle->inMemSort ? SORT_QSORT_T : SORT_SPILLED_MERGE_SORT_T;
     info.loops = pHandle->loops;
@@ -840,6 +844,7 @@ SSortExecInfo tsortGetSortExecInfo(SSortHandle* pHandle) {
       info.writeBytes = st.flushBytes;
       info.readBytes = st.loadBytes;
     }
+  }
 
   return info;
 }