Re: MultiXact\SLRU buffers configuration

On Wed, Aug 21, 2024 at 12:46:31PM +0900, Michael Paquier wrote:
> Sorry, I should have split that for clarity (one patch for the GUC,
> one to change the test to use CACHED/LOAD). It is not an error
> though: if we don't have a controlled way to disable the stats of the
> module, then the test would fail when calling the cached callback
> because we'd try to allocate some memory for the dshash entry in
> pgstats.
>
> The second effect of initializing the shmem state of the module with
> shared_preload_libraries is condition variables are set up for the
> sake if the test, removing the dependency to the SQL load() call.
> Both are OK, but I'd prefer introducing one use case for these two
> macros in the tree, so as these can be used as a reference in the
> future when developing new tests.

In short, here is a better patch set, with 0001 and 0002 introducing
the pieces that the test would need to be able to use the LOAD() and
CACHED() macros in 0003:
- 0001: Add shmem callbacks to initialize shmem state of
injection_points with shared_preload_libraries.
- 0002: Add a GUC to control if the stats of the module are enabled.
By default, they are disabled as they are only needed in the TAP test
of injection_points for the stats.
- 0003: Update the SLRU test to use INJECTION_POINT_LOAD and
INJECTION_POINT_CACHED with injection_points loaded via
shared_preload_libraries, removing the call to
injection_points_load() in the perl test.

What do you think?
--
Michael