Re: PATCH: logical_work_mem and logical streaming of large in-progress transactions

On Wed, Apr 28, 2021 at 11:00 AM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> Tom Lane has raised a complaint on pgsql-commiters [1] about one of
> the commits related to this work [2]. The new member wrasse is showing
> Warning:
>
> "/export/home/nm/farm/studio64v12_6/HEAD/pgsql.build/../pgsql/src/backend/replication/logical/reorderbuffer.c",
> line 2510: Warning: Likely null pointer dereference (*(curtxn+272)):
> ReorderBufferProcessTXN
>
> The Warning is for line:
> curtxn->concurrent_abort = true;
>
> Now, we can simply fix this warning by adding an if check like:
> if (curtxn)
> curtxn->concurrent_abort = true;
>
> However, on further discussion, it seems that is not sufficient here
> because the callbacks can throw the surrounding error code
> (ERRCODE_TRANSACTION_ROLLBACK) where we set concurrent_abort flag for
> a completely different scenario. I think here we need a
> stronger check to ensure that we set concurrent abort flag and do
> other things in that check only when we are decoding non-committed
> xacts.

That makes sense.

The idea I have is to additionally check that we are decoding
> streaming or prepared transaction (the same check as we have for
> setting curtxn) or we can check if CheckXidAlive is a valid
> transaction id. What do you think?

I think a check based on CheckXidAlive looks good to me. This will
protect against if a similar error is raised from any other path as
you mentioned above.

--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com