Re: pg_upgrade version checking questions

From: Daniel Gustafsson <daniel(at)yesql(dot)se>
To: Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>
Cc: "pgsql-hackers(at)lists(dot)postgresql(dot)org" <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: pg_upgrade version checking questions
Date: 2021-02-23 16:14:28
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> On 27 Jul 2019, at 08:42, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com> wrote:
> On 2019-07-25 16:33, Daniel Gustafsson wrote:
>> Fair enough, those are both excellent points. I’ve shuffled the code around to
>> move back the check for exec_path to setup (albeit earlier than before due to
>> where we perform directory checking). This does mean that the directory
>> checking in the options parsing must learn to cope with missing directories,
>> which is a bit unfortunate since it’s already doing a few too many things IMHO.
>> To ensure dogfooding, I also removed the use of -B in ‘make check’ for
>> pg_upgrade, which should bump the coverage.
>> Also spotted a typo in a pg_upgrade file header in a file touched by this, so
>> included it in this thread too as a 0004.
> I have committed 0002, 0003, and 0004.
> The implementation in 0001 (Only allow upgrades by the same exact
> version new bindir) has a problem. It compares (new_cluster.bin_version
> != PG_VERSION_NUM), but new_cluster.bin_version is actually just the
> version of pg_ctl, so this is just comparing the version of pg_upgrade
> with the version of pg_ctl, which is not wrong, but doesn't really
> achieve the full goal of having all binaries match.
> I think a better structure would be to add a version check for each
> validate_exec() so that each program is checked against pg_upgrade.
> This should mirror what find_other_exec() in src/common/exec.c does. In
> a better world we would use find_other_exec() directly, but then we
> can't support -B. Maybe expand find_other_exec() to support this, or
> make a private copy for pg_upgrade to support this. (Also, we have two
> copies of validate_exec() around. Maybe this could all be unified.)

Turns out I overshot my original estimate of a new 0001 by a hair (by ~530 days
or so) but attached is an updated version.

This exports validate_exec to reduce duplication, and implements a custom
find_other_exec-like function in pg_upgrade to check each binary for the
version number. Keeping a local copy of validate_exec is easy to do if it's
deemed not worth it to export it.

Daniel Gustafsson

Attachment Content-Type Size
v5-0001-Check-version-of-target-cluster-binaries.patch application/octet-stream 5.9 KB

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