nix: UTC by default for postgrest-with-postgresql

[steve-chavez]

Fixes unreliable output on tests, see #2523 (comment)

[wolfgangwalther]

What does adding this do?

Or did you want to use $PGTZ below in the -c timezone= addition?

[steve-chavez]

I was mostly adding it for documentation purposes. PGTZ is pg env var: https://www.postgresql.org/docs/current/libpq-envars.html

So I can do:

PGTZ=EST postgrest-with-postgresql-15 psql

select now()

And get the correct time for my timezone.

[steve-chavez]

It does override the -c timezone, I tested it.

[wolfgangwalther]

Hm. Doesn't that mean that at least one of the two is redundant, then?

[steve-chavez]

Hm, I don't see it that way. PGTZ is for overriding and -c timezone=utc is for the default.

The problem on #2523 (comment) was that running postgrest-test-spec failed locally and not on CI and that was confusing.

[steve-chavez]

Open to hear better alternatives, not sure what would be the issue with the current setup though.

[wolfgangwalther]

PGTZ is for overriding

But it doesn't do it. If you remove the ARG_USE_ENV line - it will still override, when you explicitly set PGTZ before calling postgrest-with-postgresql-xx.

So this line is just unused in it's current form, especially the default value you give on that line, too. Try changing the default in the ARG_USE_ENV line - it doesn't have any effect. Or in other words, you currently have two default values: One in the ARG_USE_ENV, one in the -c timezone=. Obviously, only one default can actually "work", right?

There's two ways to actually use PGTZ in the nix script, too:

"ARG_USE_ENV([PGTZ], [utc], [Timezone to use])"
...
export PGTZ

Doing it this way, you don't need the -c timezone=utc anymore. PGTZ will be used from the outside - and if not set, the default utc will be used as given in the ARG_USE_ENV line. PGTZ will then be passed to any client that uses the temporary database.

I think this is the cleanest approach.

---

The other way would be like this:

"ARG_USE_ENV([PGTZ], [utc], [Timezone to use])"
...
-c timezone="$PGTZ"

This would make the the default for PGTZ only available within the current script - but then set it as the default via server-side configuration.

[steve-chavez]

Ok, cool. Fixed according to approach 1 on #2674