Horton

Re: Backporting BackgroundPsql

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Heikki Linnakangas <hlinnaka@iki.fi>
Cc: PostgreSQL Hackers <pgsql-hackers@postgresql.org>, Daniel Gustafsson <daniel@yesql.se>, Andrew Dunstan <andrew@dunslane.net>, Melanie Plageman <melanieplageman@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, Mikael Kjellström <mikael.kjellstrom@gmail.com>
Date: 2024-06-25T11:40:38Z
Lists: pgsql-hackers 
Hi,

On 2024-06-25 13:26:23 +0300, Heikki Linnakangas wrote:
> While fixing a recent bug on visibility on a standby [1], I wrote a
> regression test that uses BackgroundPsql to run some queries in a
> long-running psql session. The problem is that that was refactored in v17,
> commit 664d757531. The test I wrote for v17 doesn't work as it is on
> backbranches. Options:
> 
> 1. Write the new test differently on backbranches. Before 664d757531, the
> test needs to work a lot harder to use the background psql session, calling
> pump() etc. That's doable, but as noted in the discussion that led to
> 664d757531, it's laborious and error-prone.
> 
> 2. Backport commit 664d757531. This might break out-of-tree perl tests that
> use the background_psql() function. I don't know if any such tests exist,
> and they would need to be changed for v17 anyway, so that seems acceptable.
> Anyone aware of any extensions using the perl test modules?
> 
> 3. Backport commit 664d757531, but keep the existing background_psql()
> function unchanged. Add a different constructor to get the v17-style
> BackgroundPsql session, something like "$node->background_psql_new()".
> 
> I'm leaning towards 3. We might need to backport more perl tests that use
> background_psql() in the future, backporting the test module will make that
> easier.
> 
> Thoughts?

Yes, I've wished for this a couple times. I think 2 or 3 would be reasonable.
I think 1) often just leads to either tests not being written or being
fragile...

Greetings,

Andres Freund

Commits

  1. Fix missing installation/uninstallation rules for BackgroundPsql.pm

  2. Backport BackgroundPsql perl test module

  3. Add missing uninstallation rule for BackgroundPsql.pm

  4. Fix missing installation rules for BackgroundPsql.pm

  5. Skip \password TAP test on old IPC::Run versions

  6. Test SCRAM iteration changes with psql \password

  7. Refactor background psql TAP functions