Craig Ringer <craig@2ndquadrant.com> writes: > It's sometimes desirable to collect auto_explain data with ANALYZE in order > to track down hard-to-reproduce issues, but the performance impacts can be > pretty hefty on the DB.
> I'm inclined to add a sample rate to auto_explain so that it can trigger > only on x percent of queries,
That sounds reasonable ...
Cool, I'll cook that up then. Thanks for the sanity check.
> and also add a sample test hook that can be > used to target statements of interest more narrowly (using a C hook > function).
You'd have to be pretty desperate, *and* knowledgeable, to write a C function for that. Can't we invent something a bit more user-friendly for the purpose? No idea what it should look like though.
I've been that desperate.
For the majority of users I'm sure it's sufficient to just have a sample rate.
Anything that's trying to match individual queries could be interested in all sorts of different things. Queries that touch a particular table being one of the more obvious things, or queries that mention a particular literal. Rather than try to design something complicated in advance that anticipates all needs, I'm thinking it makes sense to just throw a hook in there. If some patterns start to emerge in terms of useful real world filtering criteria then that'd better inform any more user accessible design down the track.