Anssi Kääriäinen<anssi.kaariai...@thl.fi> wrote: > So, count(*) queries are more than twice as slow compared to the > old serializable transaction isolation level. I've looked at this enough to know that I can do something about that, but wanted to point out that this is a good example of why you should specify READ ONLY when possible. My numbers: begin transaction isolation level repeatable read; Time: 394.946 ms Time: 248.675 ms Time: 242.559 ms
begin transaction isolation level serializable; Time: 494.676 ms Time: 494.036 ms Time: 491.712 ms begin transaction isolation level serializable, read only; Time: 234.075 ms Time: 234.050 ms Time: 234.057 ms begin transaction isolation level serializable, read only, deferrable; Time: 233.494 ms Time: 234.099 ms Time: 235.290 ms The slower times for REPEATABLE READ gave me pause, so I ran those again: begin transaction isolation level repeatable read; Time: 233.946 ms Time: 236.200 ms Time: 236.414 ms I guess the database just hadn't "warmed up" enough for the first few tests.... -Kevin -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
