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>, pgsql-hackers <pgsql-hackers@postgresql.org>, Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp>
Date: 2021-05-06T03:43:32Z
Lists: pgsql-hackers

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On Mon, May 3, 2021 at 9:18 PM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
>
> On Mon, May 3, 2021 at 2:27 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> > Apart from this, I think you
> > have suggested somewhere in this thread to slightly update the
> > description of stream_bytes. I would like to update the description of
> > stream_bytes and total_bytes as below:
> >
> > stream_bytes
> > Amount of transaction data decoded for streaming in-progress
> > transactions to the decoding output plugin while decoding changes from
> > WAL for this slot. This and other streaming counters for this slot can
> > be used to tune logical_decoding_work_mem.
> >
> > total_bytes
> > Amount of transaction data decoded for sending transactions to the
> > decoding output plugin while decoding changes from WAL for this slot.
> > Note that this includes data that is streamed and/or spilled.
> >
> > This update considers two points:
> > a. we don't send this data across the network because plugin might
> > decide to filter this data, ex. based on publications.
> > b. not all of the decoded changes are sent to plugin, consider
> > REORDER_BUFFER_CHANGE_INTERNAL_COMMAND_ID,
> > REORDER_BUFFER_CHANGE_INTERNAL_SNAPSHOT, etc.
>
> Looks good to me.

Attached the doc update patch.

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.