Re: Parallel scan with SubTransGetTopmostTransaction assert coredump

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