From 83d9d4d16bf72e7443dc0ce962a940cb4077a034 Mon Sep 17 00:00:00 2001
From: HuaiyuXu <xuhuaiyu@pingcap.com>
Date: Tue, 12 Mar 2019 20:59:15 +0800
Subject: [PATCH] planner, executor: check col.OrigColName instead of
 col.ColName in isCoveringIndex (#9637) (#9658)

---
 executor/executor_test.go            |  6 ++++++
 planner/core/find_best_task.go       |  4 +++-
 planner/core/logical_plan_builder.go | 13 +++++++------
 3 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/executor/executor_test.go b/executor/executor_test.go
index c2662d33c1027..878cfd56c9857 100644
--- a/executor/executor_test.go
+++ b/executor/executor_test.go
@@ -1289,6 +1289,12 @@ func (s *testSuite) TestIndexScan(c *C) {
 	tk.MustExec("create table t(a varchar(50) primary key, b int, c int, index idx(b))")
 	tk.MustExec("insert into t values('aa', 1, 1)")
 	tk.MustQuery("select * from t use index(idx) where a > 'a'").Check(testkit.Rows("aa 1 1"))
+
+	// fix issue9636
+	tk.MustExec("drop table if exists t")
+	tk.MustExec("CREATE TABLE `t` (a int, KEY (a))")
+	result = tk.MustQuery(`SELECT * FROM (SELECT * FROM (SELECT a as d FROM t WHERE a IN ('100')) AS x WHERE x.d < "123" ) tmp_count"`)
+	result.Check(testkit.Rows())
 }
 
 func (s *testSuite) TestIndexReverseOrder(c *C) {
diff --git a/planner/core/find_best_task.go b/planner/core/find_best_task.go
index 024ada9e8d1b2..e4fe91ee11501 100644
--- a/planner/core/find_best_task.go
+++ b/planner/core/find_best_task.go
@@ -424,7 +424,9 @@ func isCoveringIndex(columns []*expression.Column, indexColumns []*model.IndexCo
 		isIndexColumn := false
 		for _, indexCol := range indexColumns {
 			isFullLen := indexCol.Length == types.UnspecifiedLength || indexCol.Length == col.RetType.Flen
-			if col.ColName.L == indexCol.Name.L && isFullLen {
+			// We use col.OrigColName instead of col.ColName.
+			// Related issue: https://github.com/pingcap/tidb/issues/9636.
+			if col.OrigColName.L == indexCol.Name.L && isFullLen {
 				isIndexColumn = true
 				break
 			}
diff --git a/planner/core/logical_plan_builder.go b/planner/core/logical_plan_builder.go
index 2e71162b7641e..ee4b1084e8d0b 100644
--- a/planner/core/logical_plan_builder.go
+++ b/planner/core/logical_plan_builder.go
@@ -1873,12 +1873,13 @@ func (b *planBuilder) buildDataSource(tn *ast.TableName) (LogicalPlan, error) {
 	for _, col := range columns {
 		ds.Columns = append(ds.Columns, col.ToInfo())
 		newCol := &expression.Column{
-			UniqueID: b.ctx.GetSessionVars().AllocPlanColumnID(),
-			DBName:   dbName,
-			TblName:  tableInfo.Name,
-			ColName:  col.Name,
-			ID:       col.ID,
-			RetType:  &col.FieldType,
+			UniqueID:    b.ctx.GetSessionVars().AllocPlanColumnID(),
+			DBName:      dbName,
+			TblName:     tableInfo.Name,
+			ColName:     col.Name,
+			OrigColName: col.Name,
+			ID:          col.ID,
+			RetType:     &col.FieldType,
 		}
 
 		if tableInfo.PKIsHandle && mysql.HasPriKeyFlag(col.Flag) {