Re: Parallel scan with SubTransGetTopmostTransaction assert coredump

Andres Freund <andres@anarazel.de>

From: Andres Freund <andres@anarazel.de>

To: Pengchengliu <pengchengliu@tju.edu.cn>

Cc: pgsql-hackers@postgresql.org

Date: 2021-05-07T03:55:10Z

Lists: pgsql-hackers

Hi,

On 2021-05-07 11:32:57 +0800, Pengchengliu wrote:
> Hi Hackers，
> 
> Last email, format error, missing some information, so I resend this email.  
> 
>  With PG 13.2(3fb4c75e857adee3da4386e947ba58a75f3e74b7), I tested subtransaction with parallel scan, I got a subtransaction coredump as below:


> So the root cause is the Parallel Workers process set the TransactionXmin with later transcation snapshot. When parallel scan, Parallel Workers process use the older active snapshot.
> 
> It leads to subtrans assert coredump. I don't know how to fix it. Is there any ideas?

Do you have steps to reliably reproduce this?

Greetings,

Andres Freund

Commits

Fix broken snapshot handling in parallel workers.
- 96f6ef9fe451 10.19 landed
- 198cf81e2c64 11.14 landed
- f4b77e82ebf4 12.9 landed
- bc062cb93823 13.5 landed
- 11c1239881b3 14.0 landed
- a780b2fcce6c 15.0 landed
Doc: move some catalogs.sgml entries to the right place.
- 713a431c781f 14.0 cited
Stamp 13.2.
- 3fb4c75e857a 13.2 cited
Create an infrastructure for parallel computation in PostgreSQL.
- 924bcf4f16d5 9.5.0 cited