On Thu, Dec 5, 2013 at 3:50 PM, Josh Berkus <[email protected]> wrote: > There are fairly well researched algorithms for block-based sampling > which estimate for the skew introduced by looking at consecutive rows in > a block. In general, a minimum sample size of 5% is required, and the > error is no worse than our current system. However, the idea was shot > down at the time, partly because I think other hackers didn't get the math.
I think that this certainly warrants revisiting. The benefits would be considerable. Has anyone ever thought about opportunistic ANALYZE piggy-backing on other full-table scans? That doesn't really help Greg, because his complaint is mostly that a fresh ANALYZE is too expensive, but it could be an interesting, albeit risky approach. Opportunistically/unpredictably acquiring a ShareUpdateExclusiveLock would be kind of weird, for one thing, but if a full table scan really is very expensive, would it be so unreasonable to attempt to amortize that cost? -- Peter Geoghegan -- Sent via pgsql-hackers mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
