This is an automated cherry-pick of pingcap#46310

Signed-off-by: ti-chi-bot <ti-community-prow-bot@tidb.io>

executor/tiflashtest/BUILD.bazel

@@ -9,7 +9,11 @@ go_test(
     ],
     flaky = True,
     race = "on",
+<<<<<<< HEAD:executor/tiflashtest/BUILD.bazel
     shard_count = 37,
+=======
+    shard_count = 39,
+>>>>>>> 4facc136b5e (planner: fix wrong result when pushing Agg down through Union in MPP plans (#46310)):executor/test/tiflashtest/BUILD.bazel
     deps = [
         "//config",
         "//domain",

executor/tiflashtest/tiflash_test.go

@@ -1241,6 +1241,37 @@ func TestAggPushDownCountStar(t *testing.T) {
 	tk.MustQuery("select count(*) from c, o where c.c_id=o.c_id").Check(testkit.Rows("5"))
 }
 
+func TestAggPushDownUnionAndMPP(t *testing.T) {
+	store := testkit.CreateMockStore(t, withMockTiFlash(2))
+	tk := testkit.NewTestKit(t, store)
+
+	tk.MustExec("use test")
+	tk.MustExec("create table t (a int, b int)")
+	tk.MustExec("alter table t set tiflash replica 1")
+	tk.MustExec("insert into t values (1, 1);")
+	tk.MustExec("insert into t values (1, 1);")
+	tk.MustExec("insert into t values (1, 1);")
+	tk.MustExec("insert into t values (1, 1);")
+	tk.MustExec("insert into t values (1, 1);")
+	tk.MustExec("set @@tidb_allow_mpp=1;")
+	tk.MustExec("set @@tidb_enforce_mpp=1;")
+	tk.MustExec("set @@tidb_opt_agg_push_down=1")
+
+	tk.MustExec("create table c(c_id int)")
+	tk.MustExec("create table o(o_id int, c_id int)")
+	tk.MustExec("insert into c values(1),(1),(1),(1)")
+	tk.MustExec("insert into o values(1,1),(1,1),(1,2)")
+	tk.MustExec("alter table c set tiflash replica 1")
+	tk.MustExec("alter table o set tiflash replica 1")
+
+	tk.MustQuery("select a, count(*) from (select a, b from t " +
+		"union all " +
+		"select a, b from t" +
+		") t group by a order by a limit 10;").Check(testkit.Rows("1 10"))
+
+	tk.MustQuery("select o.o_id, count(*) from c, o where c.c_id=o.o_id group by o.o_id").Check(testkit.Rows("1 12"))
+}
+
 func TestGroupStreamAggOnTiFlash(t *testing.T) {
 	store := testkit.CreateMockStore(t, withMockTiFlash(2))
 	tk := testkit.NewTestKit(t, store)

planner/core/casetest/enforce_mpp_test.go

@@ -345,13 +345,20 @@ func TestMPP2PhaseAggPushDown(t *testing.T) {
 	tk.MustExec("create table c(c_id bigint)")
 	tk.MustExec("create table o(o_id bigint, c_id bigint not null)")
 
+	tk.MustExec("create table t (a int, b int)")
+	tk.MustExec("insert into t values (1, 1);")
+	tk.MustExec("insert into t values (1, 1);")
+	tk.MustExec("insert into t values (1, 1);")
+	tk.MustExec("insert into t values (1, 1);")
+	tk.MustExec("insert into t values (1, 1);")
+
 	// Create virtual tiflash replica info.
 	dom := domain.GetDomain(tk.Session())
 	is := dom.InfoSchema()
 	db, exists := is.SchemaByName(model.NewCIStr("test"))
 	require.True(t, exists)
 	for _, tblInfo := range db.Tables {
-		if tblInfo.Name.L == "c" || tblInfo.Name.L == "o" {
+		if tblInfo.Name.L == "c" || tblInfo.Name.L == "o" || tblInfo.Name.L == "t" {
 			tblInfo.TiFlashReplica = &model.TiFlashReplicaInfo{
 				Count:     1,
 				Available: true,