planner: the recursive cte will make UPDATE's result wrong (#49400)

close pingcap/tidb#48969

pkg/planner/core/logical_plan_builder.go

@@ -7731,6 +7731,10 @@ func (b *PlanBuilder) buildRecursiveCTE(ctx context.Context, cte ast.ResultSetNo
 					// Build seed part plan.
 					saveSelect := x.SelectList.Selects
 					x.SelectList.Selects = x.SelectList.Selects[:i]
+					// We're rebuilding the seed part, so we pop the result we built previously.
+					for _i := 0; _i < i; _i++ {
+						b.handleHelper.popMap()
+					}
 					p, err = b.buildSetOpr(ctx, x)
 					if err != nil {
 						return err

tests/integrationtest/r/planner/core/issuetest/planner_issue.result

@@ -313,3 +313,22 @@ a	length(a)
 select *,length(a) from t2 where a like '测试';
 a	length(a)
 测试	4
+drop view if exists v1;
+create view v1(id) as
+with recursive cte(a) as (select 1 union select a+1 from cte where a<3)
+select * from cte;
+create table test2(id int,value int);
+insert into test2 values(1,1),(2,2),(3,3),(4,4),(5,5);
+update test2
+set value=0
+where test2.id in
+(
+select * from v1
+);
+select * from test2;
+id	value
+1	0
+2	0
+3	0
+4	4
+5	5

tests/integrationtest/t/planner/core/issuetest/planner_issue.test

@@ -169,3 +169,20 @@ explain format = brief select *,length(a) from t2 where a like '测试 %';
 explain format = brief select *,length(a) from t2 where a like '测试';
 select *,length(a) from t2 where a like '测试 %';
 select *,length(a) from t2 where a like '测试';
+
+# https://github.com/pingcap/tidb/issues/48969
+drop view if exists v1;
+create view v1(id) as
+with recursive cte(a) as (select 1 union select a+1 from cte where a<3)
+select * from cte;
+
+create table test2(id int,value int);
+insert into test2 values(1,1),(2,2),(3,3),(4,4),(5,5);
+
+update test2
+set value=0
+where test2.id in
+(
+  select * from v1
+);
+select * from test2;