Re: ZStandard (with dictionaries) compression support for TOAST compression

On Tue, Jul 15, 2025 at 10:37:02PM -0700, Nikhil Kumar Veldanda wrote:
> 0001 – pg_compression_available()
> pg_compression_available() in misc.c feels sensible;

Actually, I have taken a step back on this one and recalled that the
list of values available for an enum GUC are already available in
pg_settings, so we can already do something without this function,
with the same result:
+SELECT NOT(enumvals @> '{lz4}') AS skip_test FROM pg_settings WHERE
+ name = 'default_toast_compression' \gset

> 0002 – test-suite split
> The new compression.sql / compression_lz4.sql split makes the diffs
> much easier to reason about.

Another thing that I have spent a lot of time on today while having a
second look was the code coverage after a make check. There was one
surprising result: lz4_compress_datum() for the incompressible data
case now has some coverage.

A second thing is AdjustUpgrade.pm, which has the matview compressmv
with a qual based on cmdata1, but I think we're OK as this is an
adjustment of the upgrade dumps for 74a3fc36f314, which exists in
v16~. I'll keep an eye on the buildfarm anyway, in case something
shows up.
--
Michael