Postgres in alpine has collation warning if database was created in another OS.

Postgres shows warning WARNING: database "postgres" has no actual collation version, but a version was recorded if database was created in another OS.

Steps for reproduce:

Execute postgres in debian image: docker run --rm -e POSTGRES_PASSWORD=password -e POSTGRES_DB=app -v $(pwd)/data:/var/lib/postgresql/data postgres:15.8-bookworm
Stop this
Execute postgres in alpine image: docker run --rm --name postgres -v $(pwd)/data:/var/lib/postgresql/data postgres:15.8-alpine3.20

Run psql:


$ docker exec -ti --user postgres postgres psql
WARNING:  database "postgres" has no actual collation version, but a version was recorded
psql (15.8)
Type "help" for help.

postgres=# \c app WARNING: database "app" has no actual collation version, but a version was recorded You are now connected to database "app" as user "postgres". app=#


**Research:**

I found that a warning occurs in the `CheckMyDatabase` function when comparing the collate version in the database and the current one in this [row](https://github.com/postgres/postgres/blob/REL_15_8/src/backend/utils/init/postinit.c#L461).

... if (!isnull) { char actual_versionstr; char collversionstr;

    collversionstr = TextDatumGetCString(datum);

    actual_versionstr = get_collation_actual_version(dbform->datlocprovider, dbform->datlocprovider == COLLPROVIDER_ICU ? iculocale : collate);
    if (!actual_versionstr)
        /* should not happen */
        elog(WARNING,
             "database \"%s\" has no actual collation version, but a version was recorded",
             name);
    else if (strcmp(actual_versionstr, collversionstr) != 0)

...


After calling get_collation_actual_version, the `actual_version_str` variable is NULL, because the `get_collation_actual_version` function after the preprocessor looks like:

char get_collation_actual_version(char collprovider, const char collcollate) { char *collversion = NULL;

    if (collprovider == COLLPROVIDER_LIBC &&
        pg_strcasecmp("C", collcollate) != 0 &&
        pg_strncasecmp("C.", collcollate, 2) != 0 &&
        pg_strcasecmp("POSIX", collcollate) != 0)
{
}

return collversion;

}



And it always returns NULL

docker-library / postgres

Postgres in alpine has collation warning if database was created in another OS. #1288