From 51bf61905171b87b4e1463da727fdff39dbeddd7 Mon Sep 17 00:00:00 2001
From: Zhuhe Fang <fzhedu@gmail.com>
Date: Wed, 31 Mar 2021 19:33:24 +0800
Subject: [PATCH] planner: fix set not null flag for outer join (#23727)

---
 executor/executor_test.go                |  9 +++++----
 executor/index_lookup_merge_join_test.go |  2 +-
 planner/core/rule_column_pruning.go      | 19 +------------------
 3 files changed, 7 insertions(+), 23 deletions(-)

diff --git a/executor/executor_test.go b/executor/executor_test.go
index 4c9b94dcba..925fa48815 100644
--- a/executor/executor_test.go
+++ b/executor/executor_test.go
@@ -7974,17 +7974,18 @@ func (s *testSuiteP1) TestIssue22941(c *C) {
 		PRIMARY KEY (mid),
 		KEY ind_bm_parent (ParentId,mid)
 	)`)
-
+	// mp should have more columns than m
 	tk.MustExec(`CREATE TABLE mp (
 		mpid bigint(20) unsigned NOT NULL DEFAULT '0',
 		mid varchar(50) DEFAULT NULL COMMENT '模块主键',
+		sid int,
 	PRIMARY KEY (mpid)
 	);`)
 
-	tk.MustExec(`insert into mp values("1","1");`)
+	tk.MustExec(`insert into mp values("1","1","0");`)
 	tk.MustExec(`insert into m values("0", "0");`)
-	rs := tk.MustQuery(`SELECT ( SELECT COUNT(1) FROM m WHERE ParentId = c.mid ) expand,  bmp.mpid,  bmp.mpid IS NULL,bmp.mpid IS NOT NULL FROM m c LEFT JOIN mp bmp ON c.mid = bmp.mid  WHERE c.ParentId = '0'`)
-	rs.Check(testkit.Rows("1 <nil> 1 0"))
+	rs := tk.MustQuery(`SELECT ( SELECT COUNT(1) FROM m WHERE ParentId = c.mid ) expand,  bmp.mpid,  bmp.mpid IS NULL,bmp.mpid IS NOT NULL, sid FROM m c LEFT JOIN mp bmp ON c.mid = bmp.mid  WHERE c.ParentId = '0'`)
+	rs.Check(testkit.Rows("1 <nil> 1 0 <nil>"))
 
 	rs = tk.MustQuery(`SELECT  bmp.mpid,  bmp.mpid IS NULL,bmp.mpid IS NOT NULL FROM m c LEFT JOIN mp bmp ON c.mid = bmp.mid  WHERE c.ParentId = '0'`)
 	rs.Check(testkit.Rows("<nil> 1 0"))
diff --git a/executor/index_lookup_merge_join_test.go b/executor/index_lookup_merge_join_test.go
index 4f2bd6e148..559330fcd8 100644
--- a/executor/index_lookup_merge_join_test.go
+++ b/executor/index_lookup_merge_join_test.go
@@ -10,7 +10,7 @@ import (
 	"github.com/pingcap/tidb/util/testkit"
 )
 
-func (s *testSuite9) TestIndexLookupMergeJoinHang(c *C) {
+func (s *testSuiteJoin2) TestIndexLookupMergeJoinHang(c *C) {
 	c.Assert(failpoint.Enable("github.com/pingcap/tidb/executor/IndexMergeJoinMockOOM", `return(true)`), IsNil)
 	defer func() {
 		c.Assert(failpoint.Disable("github.com/pingcap/tidb/executor/IndexMergeJoinMockOOM"), IsNil)
diff --git a/planner/core/rule_column_pruning.go b/planner/core/rule_column_pruning.go
index ef9a5b888d..5ca2600b73 100644
--- a/planner/core/rule_column_pruning.go
+++ b/planner/core/rule_column_pruning.go
@@ -303,24 +303,7 @@ func (p *LogicalJoin) extractUsedCols(parentUsedCols []*expression.Column) (left
 }
 
 func (p *LogicalJoin) mergeSchema() {
-	lChild := p.children[0]
-	rChild := p.children[1]
-	if p.JoinType == SemiJoin || p.JoinType == AntiSemiJoin {
-		p.schema = lChild.Schema().Clone()
-	} else if p.JoinType == LeftOuterSemiJoin || p.JoinType == AntiLeftOuterSemiJoin {
-		joinCol := p.schema.Columns[len(p.schema.Columns)-1]
-		p.schema = lChild.Schema().Clone()
-		p.schema.Append(joinCol)
-	} else {
-		p.schema = expression.MergeSchema(lChild.Schema(), rChild.Schema())
-		switch p.JoinType {
-		case LeftOuterJoin:
-			resetNotNullFlag(p.schema, p.children[1].Schema().Len(), p.schema.Len())
-		case RightOuterJoin:
-			resetNotNullFlag(p.schema, 0, p.children[0].Schema().Len())
-		default:
-		}
-	}
+	p.schema = buildLogicalJoinSchema(p.JoinType, p)
 }
 
 // PruneColumns implements LogicalPlan interface.