Hi, On 2025-08-26 17:06:11 +0200, Tomas Vondra wrote: > On 8/26/25 01:48, Andres Freund wrote: > > Hi, > > > > On 2025-08-25 15:00:39 +0200, Tomas Vondra wrote: > >> Thanks. Based on the testing so far, the patch seems to be a substantial > >> improvement. What's needed to make this prototype committable? > > > > Mainly some testing infrastructure that can trigger this kind of stream. The > > logic is too finnicky for me to commit it without that. > > > > So, what would that look like?
I'm thinking of something like an SQL function that accepts a relation and a series of block numbers, which creates a read stream reading the passed in block numbers. Combined with the injection points that are already used in test_aio, that should allow to test things that I don't know how to test without that. E.g. encountering an already-in-progress multi-block IO that only completes partially. > Another approach would be to test this at C level, sidestepping the > query execution entirely. We'd have a "stream generator" that just > generates a sequence of blocks of our own choosing (could be hard-coded, > some pattern, read from a file ...), and feed it into a read stream. > > But how would we measure success for these tests? I don't think we want > to look at query duration, that's very volatile. Yea, the performance effects would be harder to test, what I care more about is the error paths. Those are really hard to test interactively. Greetings, Andres Freund
