planner: keep the original join schema in predicate pushdown

cmd/explaintest/r/subquery.result

@@ -41,3 +41,8 @@ HashJoin	7992.00	root		inner join, equal:[eq(test.t.b, test.t.b) eq(test.t.c, te
 └─TableReader(Probe)	9970.03	root		data:Selection
   └─Selection	9970.03	cop[tikv]		not(isnull(test.t.a)), not(isnull(test.t.b)), not(isnull(test.t.c))
     └─TableFullScan	10000.00	cop[tikv]	table:t1	keep order:false, stats:pseudo
+drop table if exists t1, t2;
+create table t1(a int(11));
+create table t2(a decimal(40,20) unsigned, b decimal(40,20));
+select count(*) as x from t1 group by a having x not in (select a from t2 where x = t2.b);
+x

cmd/explaintest/t/subquery.test

@@ -15,3 +15,8 @@ explain format = 'brief' select t.c in (select count(*) from t s use index(idx),
 drop table if exists t;
 create table t(a int, b int, c int);
 explain format = 'brief' select a from t t1 where t1.a = (select max(t2.a) from t t2 where t1.b=t2.b and t1.c=t2.b);
+
+drop table if exists t1, t2;
+create table t1(a int(11));
+create table t2(a decimal(40,20) unsigned, b decimal(40,20));
+select count(*) as x from t1 group by a having x not in (select a from t2 where x = t2.b);

planner/core/integration_test.go

@@ -3429,6 +3429,15 @@ func (s *testIntegrationSuite) TestIssue22850(c *C) {
 	tk.MustQuery("SELECT @v:=(SELECT 1 FROM t1 t2 LEFT JOIN t1 ON t1.a GROUP BY t1.a) FROM t1").Check(testkit.Rows()) // work fine
 }
 
+func (s *testIntegrationSuite) TestJoinSchemaChange(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(11))")
+	tk.MustExec("create table t2(a decimal(40,20) unsigned, b decimal(40,20))")
+	tk.MustQuery("select count(*) as x from t1 group by a having x not in (select a from t2 where x = t2.b)").Check(testkit.Rows())
+}
+
 // #22949: test HexLiteral Used in GetVar expr
 func (s *testIntegrationSuite) TestGetVarExprWithHexLiteral(c *C) {
 	tk := testkit.NewTestKit(c, s.store)

planner/core/logical_plan_test.go

@@ -1792,7 +1792,7 @@ func (s *testPlanSuite) TestUpdateEQCond(c *C) {
 	}{
 		{
 			sql:  "select t1.a from t t1, t t2 where t1.a = t2.a+1",
-			best: "Join{DataScan(t1)->DataScan(t2)->Projection}(test.t.a,Column#25)->Projection",
+			best: "Join{DataScan(t1)->DataScan(t2)->Projection}(test.t.a,Column#25)->Projection->Projection",
 		},
 	}
 	ctx := context.TODO()

planner/core/rule_predicate_push_down.go

@@ -208,7 +208,6 @@ func (p *LogicalJoin) PredicatePushDown(predicates []expression.Expression) (ret
 	addSelection(p, lCh, leftRet, 0)
 	addSelection(p, rCh, rightRet, 1)
 	p.updateEQCond()
-	p.mergeSchema()
 	buildKeyInfo(p)
 	return ret, p.self
 }