What’s really bad is where they (or the ORM) generate a seperate select statement for each ID in a loop. Selecting thousands of rows one row at a time from an unindexed table can be hilariously slow.
And this doesn’t even get into bizarre edge cases, like how Postgres treats foo = ANY(ARRAY[‘bar’, ‘baz’]) differently than foo IN (VALUES((‘bar’), (‘baz’))). PROTIP: the latter is often MUCH faster. I’ve learned this twice this week.