Improve query for getting users for review

[Kobzol]

The previous query had a problem where if some user was missing in the review_prefs table, it would not be returned from the query. This is problematic, because for several reasons, the review_prefs table might be incomplete, and in general, it should be possible to get users even if they are not in the review_prefs table.

There is one problem with the new query though, because there is no index on the users.username column, this will result in a sequential scan on the users table. It's probably still fast enough, but I wanted to mention it.

The LEAST clause was not required, I think. The added COALESCE is needed to treat the number of PRs for people missing in review_prefs as zero, otherwise they would be again ignored.

You can experiment with this in https://onecompiler.com/postgresql/43722tb3w.

[apiraino]

The LEAST clause was not required, I think.

So in my comment I was wrong about LEAST, right? 🤔

[Kobzol]

COALESCE should return the first non-null argument, so it should be enough to do COALESCE(NULL, 100000). I don't think that you need LEAST, if the first argument to COALESCE is non-NULL, it should be returned.