From ebf13d738fc6fc909e31be4aec2ac99bfa929669 Mon Sep 17 00:00:00 2001
From: wangmm0220 <wangmm0220@gmail.com>
Date: Sun, 27 Mar 2022 17:30:30 +0800
Subject: [PATCH] [TD-14342]<fix> fix error if nchar condition in subquery like
 "select * from (select * from table) where nchar = '0'"

---
 src/query/src/qFilter.c | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/src/query/src/qFilter.c b/src/query/src/qFilter.c
index 5af5dea753..6f7e9ebf52 100644
--- a/src/query/src/qFilter.c
+++ b/src/query/src/qFilter.c
@@ -3608,16 +3608,11 @@ int32_t filterConverNcharColumns(SFilterInfo* info, int32_t rows, bool *gotNchar
       for (int32_t j = 0; j < rows; ++j) {
         char *src = FILTER_GET_COL_FIELD_DATA(fi, j);
         char *dst = FILTER_GET_COL_FIELD_DATA(&nfi, j);
-        int32_t len = 0;
-        char *varSrc = varDataVal(src);
-        size_t k = 0, varSrcLen = varDataLen(src);
-        while (k < varSrcLen && varSrc[k++] == -1) {}
-        if (k == varSrcLen) {
-          /* NULL */
-          varDataLen(dst) = (VarDataLenT) varSrcLen;
+        if(isNull(src, TSDB_DATA_TYPE_NCHAR)){
           varDataCopy(dst, src);
           continue;
-        }
+        }gi
+        int32_t len = 0;
         bool ret = taosMbsToUcs4(varDataVal(src), varDataLen(src), varDataVal(dst), bufSize, &len);
         if(!ret) {
           qError("filterConverNcharColumns taosMbsToUcs4 error");
-- 
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