From 89bb38d0a206a24a0c6c945acb8f1c5c93816a34 Mon Sep 17 00:00:00 2001
From: Yifan Xu <30385241+xuyifangreeneyes@users.noreply.github.com>
Date: Fri, 16 Jul 2021 15:01:33 +0800
Subject: [PATCH 1/2] planner: add some comment for checkOnlyFullGroupBy
 (#25769)

---
 planner/core/logical_plan_builder.go | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/planner/core/logical_plan_builder.go b/planner/core/logical_plan_builder.go
index c8a4a2e4e9a3c..bcda8eb5dcd37 100644
--- a/planner/core/logical_plan_builder.go
+++ b/planner/core/logical_plan_builder.go
@@ -2745,6 +2745,28 @@ func checkColFuncDepend(
 			Name:   colInfo.Name,
 		}
 		pIdx, err := expression.FindFieldName(p.OutputNames(), pkName)
+		// It is possible that `pIdx < 0` and here is a case.
+		// ```
+		// CREATE TABLE `BB` (
+		//   `pk` int(11) NOT NULL AUTO_INCREMENT,
+		//   `col_int_not_null` int NOT NULL,
+		//   PRIMARY KEY (`pk`)
+		// );
+		//
+		// SELECT OUTR . col2 AS X
+		// FROM
+		//   BB AS OUTR2
+		// INNER JOIN
+		//   (SELECT col_int_not_null AS col1,
+		//     pk AS col2
+		//   FROM BB) AS OUTR ON OUTR2.col_int_not_null = OUTR.col1
+		// GROUP BY OUTR2.col_int_not_null;
+		// ```
+		// When we enter `checkColFuncDepend`, `pkName.Table` is `OUTR` which is an alias, while `pkName.Name` is `pk`
+		// which is a original name. Hence `expression.FindFieldName` will fail and `pIdx` will be less than 0.
+		// Currently, when we meet `pIdx < 0`, we directly regard `primaryFuncDepend` as false and jump out. This way is
+		// easy to implement but makes only-full-group-by checker not smart enough. Later we will refactor only-full-group-by
+		// checker and resolve the inconsistency between the alias table name and the original column name.
 		if err != nil || pIdx < 0 {
 			primaryFuncDepend = false
 			break

From 1f6c6698b3237162ba18b70a31d8b80c17fd3b44 Mon Sep 17 00:00:00 2001
From: wuliuqii <34090258+wuliuqii@users.noreply.github.com>
Date: Fri, 16 Jul 2021 15:09:33 +0800
Subject: [PATCH 2/2] *: fix some errcheck (#25855)

---
 ddl/ddl_worker_test.go | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/ddl/ddl_worker_test.go b/ddl/ddl_worker_test.go
index 72fef7c96c19e..5085e4194f0d1 100644
--- a/ddl/ddl_worker_test.go
+++ b/ddl/ddl_worker_test.go
@@ -100,7 +100,10 @@ func (s *testDDLSuite) TestNotifyDDLJob(c *C) {
 		WithStore(store),
 		WithLease(testLease),
 	)
-	defer d.Stop()
+	defer func() {
+		err := d.Stop()
+		c.Assert(err, IsNil)
+	}()
 	getFirstNotificationAfterStartDDL(d)
 	// Ensure that the notification is not handled in workers `start` function.
 	d.cancel()
@@ -141,7 +144,10 @@ func (s *testDDLSuite) TestNotifyDDLJob(c *C) {
 		WithStore(store),
 		WithLease(testLease),
 	)
-	defer d1.Stop()
+	defer func() {
+		err := d1.Stop()
+		c.Assert(err, IsNil)
+	}()
 	getFirstNotificationAfterStartDDL(d1)
 	// Ensure that the notification is not handled by worker's "start".
 	d1.cancel()