panic when union a view and temporary table

[lcwangchao]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

create table t1(a int);
insert into t1 values(1);
create view tv as select * from t1;
create temporary table t1(a int);
select * from t1 union all select * from tv;

2. What did you expect to see? (Required)

no error

3. What did you see instead (Required)

TiDB root@127.0.0.1:test> select * from t1 union all select * from tv;
(1105, 'runtime error: invalid memory address or nil pointer dereference')

4. What is your TiDB version? (Required)

+--------------------------------+
| tidb_version()                 |
+--------------------------------+
| Release Version: None          |
| Edition: Community             |
| Git Commit Hash: None          |
| Git Branch: None               |
| UTC Build Time: None           |
| GoVersion: go1.20.2            |
| Race Enabled: false            |
| TiKV Min Version: 6.2.0-alpha  |
| Check Table Before Drop: false |
| Store: unistore                |
+--------------------------------+

[lcwangchao]

It is introduced by #37393 , see:

tidb/table/temptable/infoschema.go

Lines 42 to 47 in f1df935

	func DetachLocalTemporaryTableInfoSchema(is infoschema.InfoSchema) infoschema.InfoSchema {
	if attachedInfoSchema, ok := is.(*infoschema.SessionExtendedInfoSchema); ok {
	newIs := attachedInfoSchema
	newIs.LocalTemporaryTables = nil
	return newIs
	}

The infoschema's LocalTemporaryTables is removed and later the temporary table cannot be found in this inforschema .