Horton

Re: Replication slot stats misgivings

vignesh C <vignesh21@gmail.com>

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From: vignesh C <vignesh21@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Amit Kapila <amit.kapila16@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>, Andres Freund <andres@anarazel.de>, PostgreSQL-development <pgsql-hackers@postgresql.org>, Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp>
Date: 2021-05-12T04:42:20Z
Lists: pgsql-hackers 
On Wed, May 12, 2021 at 9:59 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>
> vignesh C <vignesh21@gmail.com> writes:
> > I agree with your analysis to remove that test. Attached patch has the
> > changes for the same.
>
> Is there any value in converting the test case into a TAP test that
> could be more flexible about the expected output?  I'm mainly wondering
> whether there are any code paths that this test forces the server through,
> which would otherwise lack coverage.

Removing this test does not reduce code coverage. This test is
basically to decode and check the stats again, it is kind of a
repetitive test. The problem with this test here is that when a
transaction is spilled, the statistics for the spill transaction will
be sent to the statistics collector as and when the transaction is
spilled. This test sends spill stats around 12 times. The test expects
to reset the stats and check the stats gets updated when we get the
changes. We cannot validate reset slot stats results here, as it could
be possible that in some machines the stats collector receives the
spilled transaction stats after getting reset slots. This same problem
will exist with tap tests too. So I feel it is better to remove this
test.

Regards,
Vignesh

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.