Hi! > On 15 Jun 2023, at 03:57, Vladimir Churyukin <vladi...@churyukin.com> wrote: > > Hello, > > There is often a need to test particular queries executed in the worst-case > scenario, i.e. right after a server restart or with no or minimal amount of > data in shared buffers. In Postgres it's currently hard to achieve (other > than to restart the server completely to run a single query, which is not > practical). Is there a simple way to introduce a GUC variable that makes > queries bypass shared_buffers and always read from storage? It would make > testing like that orders of magnitude simpler. I mean, are there serious > technical obstacles or any other objections to that idea in principle?
Few months ago I implemented "drop of caches" to demonstrate basic structure of shared buffers [0]. The patch is very unsafe in the form is was implemented, but if you think that functionality is really useful (it was not intended to be) I can try to do the same as extension. it worked like "SELECT FlushAllBuffers();" and what is done resembles checkpoint, but evicts every buffer that can be evicted. Obviously, emptied buffers would be immediately reused by concurrent sessions. Best regards, Andrey Borodin. [0] https://www.youtube.com/watch?v=u8BAOqeKnwY
