Re: "ERROR: could not open relation with OID 16391" error was encountered when reindexing

Thank you for your attention.

>
> Any chance you could provide minimal steps to reproduce the issue on
> an empty PG instance, ideally as a script? That's going to be helpful
> to reproduce / investigate the issue and also make sure that it's
> fixed.

I have provided a python script in the attachment to minimize the reproduction of the issue.

The specific reproduction steps are as follows:
1. Initialize the data
```
DROP TABLE IF EXISTS tbl_part;
CREATE TABLE tbl_part (a integer) PARTITION BY RANGE (a);
CREATE TABLE tbl_part_p1 PARTITION OF tbl_part FOR VALUES FROM (0) TO (10);
CREATE INDEX ON tbl_part(a);
```
2. session1 reindex and gdb break at index.c:3585
```
REINDEX INDEX tbl_part_a_idx;
```
3. session2 drop index succeed

```
DROP INDEX tbl_part_a_idx;
```
4. session1 gdb continue


Best Regards,
Fei Changhong
Alibaba Cloud Computing Ltd.