Hi, On 2022-01-21 01:06:37 +0100, Tomas Vondra wrote: > Yeah, I haven't updated some of the test output because some of those > changes are a bit wrong (and I think that's fine for a PoC patch). I > should have mentioned that in the message, though. Sorry about that.
Given that the patch hasn't been updated since January and that it's a PoC in the final CF, it seems like it should at least be moved to the next CF? Or perhaps returned? I've just marked it as waiting-on-author for now - iirc that leads to fewer reruns by cfbot once it's failing... > 2) The correlated samples are currently built using a query, executed > through SPI in a loop. So given a "driving" sample of 30k rows, we do > 30k lookups - that'll take time, even if we do that just once and cache > the results. Ugh, yea, that's going to increase overhead by at least a few factors. > I'm sure there there's room for some improvement, though - for example > we don't need to fetch all columns included in the statistics object, > but just stuff referenced by the clauses we're estimating. That could > improve chance of using IOS etc. Yea. Even just avoid avoiding SPI / planner + executor seems likely to be a big win. It seems one more of the cases where we really need logic to recognize "cheap" vs "expensive" plans, so that we only do sampling when useful. I don't think that's solved just by having a declarative syntax. Greetings, Andres Freund
