Re: [HACKERS] GSoC 2017: Foreign Key Arrays

On Wed, Mar 03, 2021 at 11:31:49PM +0200, Mark Rofail wrote:
> This is just a rebase patch since the patch is no longer applicable to the
> current master.

It doesn't just rebase: it also removes the test which was failing on windows
CI:

--- Try using the indexable operator
-SELECT * FROM FKTABLEFORARRAYGIN WHERE ftest1 @>> 5;

> Changelog:
> - v6 (compatible with current master 2020-3-3,
> commit 3769e11a31831fc2f3bd4c4a24b4f45c352fb8fb)
> * rebase to current master

I think the SELECT, when it works, is actually doing a seq scan and not using
the index. On my PC, the index scan is used until an autovacuum/analyze run,
after which it uses seqscan. I'm not sure how the other CIs all managed to run
autovacuum between creating a table and running a query on it, though.

I guess you should first run the query with "explain (costs off)" to show what
plan it's using, and add things like "SET enable_seqscan=off" as needed to
guarantee that everyone will use the same plan, regardless of minor cost
differences and vacuum timing.

--
Justin