From c2afd95c4e7dc273ae506eb8fc015c41a277c485 Mon Sep 17 00:00:00 2001
From: wangjiaming0909 <604227650@qq.com>
Date: Wed, 3 Apr 2024 10:07:02 +0800
Subject: [PATCH] fix taosd crash query ins_tags with empty nchar tag

---
 source/libs/executor/src/sysscanoperator.c       |  5 ++++-
 tests/system-test/0-others/information_schema.py | 13 ++++++++++---
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/source/libs/executor/src/sysscanoperator.c b/source/libs/executor/src/sysscanoperator.c
index 628aacf3c3..903e2f85aa 100644
--- a/source/libs/executor/src/sysscanoperator.c
+++ b/source/libs/executor/src/sysscanoperator.c
@@ -983,7 +983,10 @@ static int32_t sysTableUserTagsFillOneTableTags(const SSysTableScanInfo* pInfo,
                                                     : (3 + DBL_MANT_DIG - DBL_MIN_EXP + VARSTR_HEADER_SIZE);
         tagVarChar = taosMemoryCalloc(1, bufSize + 1);
         int32_t len = -1;
-        convertTagDataToStr(varDataVal(tagVarChar), tagType, tagData, tagLen, &len);
+        if (tagLen > 0)
+          convertTagDataToStr(varDataVal(tagVarChar), tagType, tagData, tagLen, &len);
+        else
+          len = 0;
         varDataSetLen(tagVarChar, len);
       }
     }
diff --git a/tests/system-test/0-others/information_schema.py b/tests/system-test/0-others/information_schema.py
index 63718417b4..c3d65482fc 100644
--- a/tests/system-test/0-others/information_schema.py
+++ b/tests/system-test/0-others/information_schema.py
@@ -50,10 +50,11 @@ class TDTestCase:
         self.tbnum = 20
         self.rowNum = 10
         self.tag_dict = {
-            't0':'int'
+            't0':'int',
+            't1':f'nchar({self.nchar_length})'
         }
         self.tag_values = [
-            f'1'
+            f'1', '""'
             ]
         self.binary_str = 'taosdata'
         self.nchar_str = '涛思数据'
@@ -72,7 +73,7 @@ class TDTestCase:
         tdSql.execute(f'use {self.dbname}')
         tdSql.execute(self.setsql.set_create_stable_sql(self.stbname,self.column_dict,self.tag_dict))
         for i in range(self.tbnum):
-            tdSql.execute(f"create table {self.stbname}_{i} using {self.stbname} tags({self.tag_values[0]})")
+            tdSql.execute(f"create table {self.stbname}_{i} using {self.stbname} tags({self.tag_values[0]}, {self.tag_values[1]})")
             self.insert_data(self.column_dict,f'{self.stbname}_{i}',self.rowNum)
     def count_check(self):
         tdSql.query('select count(*) from information_schema.ins_tables')
@@ -313,6 +314,11 @@ class TDTestCase:
         tdSql.error('alter cluster "activeCode" ""')
         tdSql.execute('alter cluster "activeCode" "revoked"')
 
+    def test_query_ins_tags(self):
+        sql = f'select tag_name, tag_value from information_schema.ins_tags where table_name = "{self.stbname}_0"'
+        tdSql.query(sql)
+        tdSql.checkRows(2)
+
     def run(self):
         self.prepare_data()
         self.count_check()
@@ -322,6 +328,7 @@ class TDTestCase:
         self.ins_stable_check2()
         self.ins_dnodes_check()
         self.ins_grants_check()
+        self.test_query_ins_tags()
 
 
     def stop(self):