From d455e6ac5a9a1c5c9dbe5fd145d7586f2f06708b Mon Sep 17 00:00:00 2001
From: Lingyu Song <songlingyu@pingcap.com>
Date: Tue, 21 Aug 2018 19:21:13 +0800
Subject: [PATCH] plan: fix concat in group statement (#7448)

---
 plan/logical_plan_builder.go | 7 +++++++
 plan/logical_plan_test.go    | 8 ++++++++
 2 files changed, 15 insertions(+)

diff --git a/plan/logical_plan_builder.go b/plan/logical_plan_builder.go
index 5f18b30bff543..db807b5315e11 100644
--- a/plan/logical_plan_builder.go
+++ b/plan/logical_plan_builder.go
@@ -854,6 +854,13 @@ func matchField(f *ast.SelectField, col *ast.ColumnNameExpr, ignoreAsName bool)
 		if f.AsName.L == "" || ignoreAsName {
 			if curCol, isCol := f.Expr.(*ast.ColumnNameExpr); isCol {
 				return curCol.Name.Name.L == col.Name.Name.L
+			} else if _, isFunc := f.Expr.(*ast.FuncCallExpr); isFunc {
+				// Fix issue 7331
+				// If there are some function calls in SelectField, we check if
+				// ColumnNameExpr in GroupByClause matches one of these function calls.
+				// Example: select concat(k1,k2) from t group by `concat(k1,k2)`,
+				// `concat(k1,k2)` matches with function call concat(k1, k2).
+				return strings.ToLower(f.Text()) == col.Name.Name.L
 			}
 			// a expression without as name can't be matched.
 			return false
diff --git a/plan/logical_plan_test.go b/plan/logical_plan_test.go
index c0615ffe6ed2e..d831699064374 100644
--- a/plan/logical_plan_test.go
+++ b/plan/logical_plan_test.go
@@ -1171,6 +1171,14 @@ func (s *testPlanSuite) TestValidate(c *C) {
 			sql: "select a from t having sum(avg(a))",
 			err: ErrInvalidGroupFuncUse,
 		},
+		{
+			sql: "select concat(c_str, d_str) from t group by `concat(c_str, d_str)`",
+			err: nil,
+		},
+		{
+			sql: "select concat(c_str, d_str) from t group by `concat(c_str,d_str)`",
+			err: ErrUnknownColumn,
+		},
 	}
 	for _, tt := range tests {
 		sql := tt.sql