Andy Colson <andy@xxxxxxxxxxxxxxx> writes: > On 10/18/2016 11:44 AM, Francisco Olarte wrote: >> This should be faster, but to me it seems it does a different thing. > Ah, yes, you're right, there is a bit of a difference there. If you don't want to have an implicit bias towards earlier blocks, I don't think that either standard tablesample method is really what you want. The contrib/tsm_system_rows tablesample method is a lot closer, in that it will start at a randomly chosen block, but if you just do "tablesample system_rows(1)" then you will always get the first row in whichever block it lands on, so it's still not exactly unbiased. Maybe you could select "tablesample system_rows(100)" or so and then do the order-by-random trick on that sample. This would be a lot faster than selecting 100 random rows with either built-in sample method, since the rows it grabs will be consecutive. regards, tom lane -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
