From 4fe22bcaaa4a48c55ffc0977f0584139b8ffbbd7 Mon Sep 17 00:00:00 2001
From: congqixia <congqi.xia@zilliz.com>
Date: Thu, 16 Sep 2021 20:03:50 +0800
Subject: [PATCH] Fix query task panicking (#8060)

Signed-off-by: Congqi Xia <congqi.xia@zilliz.com>
---
 internal/proxy/task.go | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/internal/proxy/task.go b/internal/proxy/task.go
index a89577e7f5..a8ff538ce2 100644
--- a/internal/proxy/task.go
+++ b/internal/proxy/task.go
@@ -2464,13 +2464,14 @@ func (qt *queryTask) PostExecute(ctx context.Context) error {
 			},
 			FieldsData: make([]*schemapb.FieldData, 0),
 		}
-		for idx, partialRetrieveResult := range retrieveResult {
+		for _, partialRetrieveResult := range retrieveResult {
 			availableQueryNodeNum++
 			if partialRetrieveResult.Ids == nil {
 				reason += "ids is nil\n"
 				continue
 			} else {
-				if idx == 0 {
+				// handles initialization, cannot use idx==0 since first result may be empty
+				if len(qt.result.FieldsData) == 0 {
 					qt.result.FieldsData = append(qt.result.FieldsData, partialRetrieveResult.FieldsData...)
 				} else {
 					for k, fieldData := range partialRetrieveResult.FieldsData {