"Ed L." <pgsql@xxxxxxxxxxxxx> writes: > So, does this sound like we just happened to get repeatedly > horribly unrepresentative random samples with stats target at > 10? Are we at the mercy of randomness here? Or is there a > better preventive procedure we can follow to systematically > identify this kind of situation? I think the real issue is that stats target 10 is too small for large tables: the samples are just not large enough to support a decent numdistinct estimate, which is the critical stat for cases such as this (ie, estimating the number of hits on a value that's not in the most-common-values list). The reason the default is currently 10 is just conservatism: it was already an order of magnitude better than what it replaced (a *single* representative value) and I didn't feel I had the evidence to justify higher values. It's become clear that the default ought to be higher, but I've still got no good fix on a more reasonable default. 100 might be too much, or then again maybe not. I encourage you to play around with default_statistics_target and see what you can learn about quality of estimates vs. planning time. regards, tom lane
