error optimization of anti smei join on daul table

[jingyugao]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. What did you do?
   If possible, provide a recipe for reproducing the error.

drop table if exists t1,t2;
create table t1( a int);
create table t2(b int);
insert into t1 value(1);
insert into t2 value(null);
select * from t1 where 1 not in (select b from t2);
select * from t1 where t1.a not in (select b from t2);

2. What did you expect to see?

both select should return empty record.

3. What did you see instead?

select * from t1 where 1 not in (select b from t2);
+------+
| a    |
+------+
|    1 |
+------+

4. What version of TiDB are you using (tidb-server -V or run select tidb_version(); on TiDB)?
   702854f

[jingyugao]

This might be same with #12065.

[jingyugao]

This is because tidb push eq(1,t2.b) down to the tableReader(t2), so the inner table return emtpy records and tryToMatch return false,false,nil
see code https://github.com/pingcap/tidb/blob/master/executor/joiner.go#L227

[ti-srebot]

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