Re: Small issues with CREATE TABLE COMPRESSION

On Wed, May 05, 2021 at 01:41:03PM +0530, Dilip Kumar wrote:
> I think we already have such test cases at least through pg_upgrade.
> Basically, if you see in compression.sql we are not dropping the table
> so that pg_upgrade and dump them and test.  So if test run --with-lz4
> then in pg_upgrade dump we can see ALTER TABLE... SET COMPRESSION type
> of commands.

The TAP tests of pg_dump are much more picky than what pg_upgrade is
able to do.  With the existing set of tests in place, what you are
able to detect is that pg_upgrade does not *break* if there are tables
with attributes using various compression types, but that would not be
enough to make sure that the correct compression method is *applied*
depending on the context expected (default_toast_compression + the
attribute compression + pg_dump options), which is what the TAP tests
of pg_dump are able to correctly detect if extended in an appropriate
way.

With what's on HEAD, we would easily miss any bugs introduced in
pg_dump that change the set of commands generated depending on the
options given by a user, but still allow pg_upgrade to work correctly.
For example, there could be issues where we finish by setting up the
incorrect compression option, with pg_upgrade happily finishing.
There is a gap in the test coverage here.
--
Michael