From 451b6a451d159440a49f353c216a3d8a8ae88b80 Mon Sep 17 00:00:00 2001
From: Minglei Jin <mljin@taosdata.com>
Date: Wed, 2 Nov 2022 11:47:58 +0800
Subject: [PATCH] fix: set output value to null if zero-length

---
 source/libs/tdb/src/db/tdbBtree.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/source/libs/tdb/src/db/tdbBtree.c b/source/libs/tdb/src/db/tdbBtree.c
index 19580d486a..e4d3cc3488 100644
--- a/source/libs/tdb/src/db/tdbBtree.c
+++ b/source/libs/tdb/src/db/tdbBtree.c
@@ -1715,16 +1715,20 @@ int tdbBtreeNext(SBTC *pBtc, void **ppKey, int *kLen, void **ppVal, int *vLen) {
   memcpy(pKey, cd.pKey, cd.kLen);
 
   if (ppVal) {
-    // TODO: vLen may be zero
-    pVal = tdbRealloc(*ppVal, cd.vLen);
-    if (pVal == NULL) {
-      tdbFree(pKey);
-      return -1;
+    if (cd.vLen > 0) {
+      pVal = tdbRealloc(*ppVal, cd.vLen);
+      if (pVal == NULL) {
+        tdbFree(pKey);
+        return -1;
+      }
+
+      memcpy(pVal, cd.pVal, cd.vLen);
+    } else {
+      pVal = NULL;
     }
 
     *ppVal = pVal;
     *vLen = cd.vLen;
-    memcpy(pVal, cd.pVal, cd.vLen);
   }
 
   ret = tdbBtcMoveToNext(pBtc);