Horton

Backporting BackgroundPsql

Heikki Linnakangas <hlinnaka@iki.fi>

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From: Heikki Linnakangas <hlinnaka@iki.fi>
To: PostgreSQL Hackers <pgsql-hackers@postgresql.org>, Daniel Gustafsson <daniel@yesql.se>
Cc: Andrew Dunstan <andrew@dunslane.net>, Andres Freund <andres@anarazel.de>, 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: 2024-06-25T10:26:23Z
Lists: pgsql-hackers 
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?

[1] 
https://www.postgresql.org/message-id/6b852e98-2d49-4ca1-9e95-db419a2696e0@iki.fi

-- 
Heikki Linnakangas
Neon (https://neon.tech)

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