On 12 August 2016 at 18:54, Tom Lane <t...@sss.pgh.pa.us> wrote: > Simon Riggs <si...@2ndquadrant.com> writes: >> On 12 August 2016 at 16:23, Tom Lane <t...@sss.pgh.pa.us> wrote: >>> I think "global" might have implications we don't want. How about >>> adding ", based on a system-generated seed"? > >> What I was trying to express was that > >> SELECT setseed(dp); >> SELECT * FROM foo TABLESAMPLE ...; >> SELECT * FROM foo TABLESAMPLE ...; >> SELECT * FROM foo TABLESAMPLE ...; > >> would yield a repeatable set of samples, similarly repeatable but not >> same samples as > >> SELECT * FROM foo TABLESAMPLE ... REPEATABLE; >> SELECT * FROM foo TABLESAMPLE ... REPEATABLE; >> SELECT * FROM foo TABLESAMPLE ... REPEATABLE; > > But that's *wrong*. Not all tablesample methods make any such guarantee. > In fact, neither of our contrib methods do. Only if you use REPEATABLE > (and the method allows it) is there any promise at all about repeatability.
OK, fair enough. I'll just use your wording then. Thanks. -- Simon Riggs http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services -- Sent via pgsql-docs mailing list (pgsql-docs@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-docs
