planner: outer join elimination doesn't consider the ORDER BY items f…

…rom the agg func (#38380) (#39024) close #18216
pingcap · Nov 9, 2022 · 33261f2 · 33261f2
1 parent 4d1a71c
commit 33261f2
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diff --git a/planner/core/integration_test.go b/planner/core/integration_test.go
@@ -1538,6 +1538,19 @@ func (s *testIntegrationSuite) TestIndexMergeHint4CNF(c *C) {
 	}
 }
 
+func (s *testIntegrationSuite) TestOuterJoinEliminationForIssue18216(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t1, t2;")
+	tk.MustExec("create table t1 (a int, c int);")
+	tk.MustExec("insert into t1 values (1, 1), (1, 2), (2, 3), (2, 4);")
+	tk.MustExec("create table t2 (a int, c int);")
+	tk.MustExec("insert into t2 values (1, 1), (1, 2), (2, 3), (2, 4);")
+	// The output might be unstable.
+	tk.MustExec("select group_concat(c order by (select group_concat(c order by a) from t2 where a=t1.a)) from t1; ")
+	tk.MustQuery("select group_concat(c order by (select group_concat(c order by c) from t2 where a=t1.a), c desc) from t1;").Check(testkit.Rows("2,1,4,3"))
+}
+
 func (s *testIntegrationSuite) TestInvisibleIndex(c *C) {
 	tk := testkit.NewTestKit(c, s.store)
 

diff --git a/planner/core/rule_join_elimination.go b/planner/core/rule_join_elimination.go
@@ -206,6 +206,9 @@ func (o *outerJoinEliminator) doOptimize(p LogicalPlan, aggCols []*expression.Co
 			for _, expr := range aggDesc.Args {
 				parentCols = append(parentCols, expression.ExtractColumns(expr)...)
 			}
+			for _, byItem := range aggDesc.OrderByItems {
+				parentCols = append(parentCols, expression.ExtractColumns(byItem.Expr)...)
+			}
 		}
 	default:
 		parentCols = append(parentCols[:0], p.Schema().Columns...)