Horton

Re: Replication slot stats misgivings

Masahiko Sawada <sawada.mshk@gmail.com>

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From: Masahiko Sawada <sawada.mshk@gmail.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: vignesh C <vignesh21@gmail.com>, Andres Freund <andres@anarazel.de>, PostgreSQL-development <pgsql-hackers@postgresql.org>, Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp>
Date: 2021-04-28T11:21:21Z
Lists: pgsql-hackers

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On Wed, Apr 28, 2021 at 6:39 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> On Wed, Apr 28, 2021 at 12:49 PM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
> >
> >
> > BTW regarding the commit f5fc2f5b23 that added total_txns and
> > total_bytes, we add the reorder buffer size (i.g., rb->size) to
> > rb->totalBytes but I think we should use the transaction size (i.g.,
> > txn->size) instead:
> >
>
> You are right about the problem but I think your proposed fix also
> won't work because txn->size always has current transaction size which
> will be top-transaction in the case when a transaction has multiple
> subtransactions. It won't include the subtxn->size.

Right. I missed the point that ReorderBufferProcessTXN() processes
also subtransactions.

> I think we can fix it by keeping track of total_size in toptxn as we
> are doing for the streaming case in ReorderBufferChangeMemoryUpdate.
> We can probably do it for non-streaming cases as well.

Agreed.

I've updated the patch. What do you think?

Regards,


--
Masahiko Sawada
EDB:  https://www.enterprisedb.com/

Commits

  1. Doc: Update logical decoding stats information.

  2. Fix tests for replication slots stats.

  3. Update replication statistics after every stream/spill.

  4. Fix the computation of slot stats for 'total_bytes'.

  5. Another try to fix the test case added by commit f5fc2f5b23.

  6. Use HTAB for replication slot statistics.

  7. Fix test case added by commit f5fc2f5b23.

  8. Add information of total data processed to replication slot stats.

  9. Use NameData datatype for slotname in stats.