From: | Peter Smith <smithpb2250(at)gmail(dot)com> |
---|---|
To: | "Zhijie Hou (Fujitsu)" <houzj(dot)fnst(at)fujitsu(dot)com> |
Cc: | shveta malik <shveta(dot)malik(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Nisha Moond <nisha(dot)moond412(at)gmail(dot)com>, "Hayato Kuroda (Fujitsu)" <kuroda(dot)hayato(at)fujitsu(dot)com> |
Subject: | Re: Collect statistics about conflicts in logical replication |
Date: | 2024-08-30 05:23:04 |
Message-ID: | CAHut+PvPDrxLNNjTOnkOMTsYtP-HQ=vWnyuU=WMfOdXK3Y+2GQ@mail.gmail.com |
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Lists: | pgsql-hackers |
Hi Hou-San. Here are my review comments for v4-0001.
======
1. Add links in the docs
IMO it would be good for all these confl_* descriptions (in
doc/src/sgml/monitoring.sgml) to include links back to where each of
those conflict types was defined [1].
Indeed, when links are included to the original conflict type
information then I think you should remove mentioning
"track_commit_timestamp":
+ counted only when the
+ <link linkend="guc-track-commit-timestamp"><varname>track_commit_timestamp</varname></link>
+ option is enabled on the subscriber.
It should be obvious that you cannot count a conflict if the conflict
does not happen, but I don't think we should scatter/duplicate those
rules in different places saying when certain conflicts can/can't
happen -- we should just link everywhere back to the original
description for those rules.
~~~
2. Arrange all the counts into an intuitive/natural order
There is an intuitive/natural ordering for these counts. For example,
the 'confl_*' count fields are in the order insert -> update ->
delete, which LGTM.
Meanwhile, the 'apply_error_count' and the 'sync_error_count' are not
in a good order.
IMO it makes more sense if everything is ordered as:
'sync_error_count', then 'apply_error_count', then all the 'confl_*'
counts.
This comment applies to lots of places, e.g.:
- docs (doc/src/sgml/monitoring.sgml)
- function pg_stat_get_subscription_stats (pg_proc.dat)
- view pg_stat_subscription_stats (src/backend/catalog/system_views.sql)
- TAP test SELECTs (test/subscription/t/026_stats.pl)
As all those places are already impacted by this patch, I think it
would be good if (in passing) we (if possible) also swapped the
sync/apply counts so everything is ordered intuitively top-to-bottom
or left-to-right.
Kind Regards,
Peter Smith.
Fujitsu Australia
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