diff --git a/src/plugins/http/src/httpGcJson.c b/src/plugins/http/src/httpGcJson.c
index 2d361d37940a93c3627ef53883a342d12183e6a1..c5b5a20cbcbbb05d70cfa094105a4a32da197469 100644
--- a/src/plugins/http/src/httpGcJson.c
+++ b/src/plugins/http/src/httpGcJson.c
@@ -129,7 +129,7 @@ bool gcBuildQueryJson(HttpContext *pContext, HttpSqlCmd *cmd, TAOS_RES *result,
 
     // for group by
     if (groupFields != -1) {
-      char    target[HTTP_GC_TARGET_SIZE] = {0};
+      char    target[HTTP_GC_TARGET_SIZE << 5] = {0};
       int32_t len;
       len = snprintf(target, HTTP_GC_TARGET_SIZE, "%s{", aliasBuffer);
       for (int32_t i = dataFields + 1; i < num_fields; i++) {
@@ -167,7 +167,7 @@ bool gcBuildQueryJson(HttpContext *pContext, HttpSqlCmd *cmd, TAOS_RES *result,
           case TSDB_DATA_TYPE_NCHAR:
             if (row[i] != NULL) {
               len += snprintf(target + len, HTTP_GC_TARGET_SIZE - len, "%s:", fields[i].name);
-              memcpy(target + len, (char *)row[i], length[i]);
+              memcpy(target + len, (char *)row[i], MIN(length[i], HTTP_GC_TARGET_SIZE - 1 - len));
               len = (int32_t)strlen(target);
             }
             break;
diff --git a/tests/script/general/http/grafana.sim b/tests/script/general/http/grafana.sim
index 414b859bd3dcaa78ab7d814afd660c9894857cc3..0b9460c08c961cc9e1fc404db1aff0d862179716 100644
--- a/tests/script/general/http/grafana.sim
+++ b/tests/script/general/http/grafana.sim
@@ -50,6 +50,9 @@ sql insert into t3 values('2017-12-25 21:25:41', 3)
 sql insert into t3 values('2017-12-25 21:26:41', 3)
 sql insert into t3 values('2017-12-25 21:27:41', 3)
 
+sql create table m3 (ts timestamp, col1 int, col2 float, txt binary(500))
+sql insert into m3 values(now, 1, 2.0, 'HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS')
+
 print ===============  step2 - login
 
 system_content curl 127.0.0.1:7111/grafana/
@@ -179,4 +182,10 @@ if $system_content != @[{"refId":"A","target":"{count(v1):3}","datapoints":[[15.
   return -1
 endi
 
-system sh/exec.sh -n dnode1 -s stop -x SIGINT
\ No newline at end of file
+system_content curl -H 'Authorization: Taosd /KfeAzX/f9na8qdtNZmtONryp201ma04bEl8LcvLUd7a8qdtNZmtONryp201ma04' -d '[{"refId":"A","alias":"taosd","sql":"select last(col1), last(col2), last(txt) from d1.m3 group by txt"}]' 127.0.0.1:7111/grafana/query
+print 20-> $system_content
+if $system_content != @[{"refId":"A","target":"taosd{last(col2):2.00000, last(txt):HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HELLO TAOS HE","datapoints":[[1,"-"]]}]@ then
+  return -1
+endi
+
+system sh/exec.sh -n dnode1 -s stop -x SIGINT