Rafael Martinez wrote:
One thing I miss from the statistics you can get via pg_stat_* is information about how long we have been collecting stats (or in other words, when was the last time the stats were reset)
I've considered adding this for the same reasons you're asking about it, but am not happy with the trade-offs involved. The problem is that you have to presume the server was running the entirety of the time since stats were reset for that data to be useful. So unless people are in that situation, they're going to get data that may not represent what they think it does. Realistically, if you want a timestamp that always means something useful you have to rest the stats at every server start, which leads us to:
Before 8.3, we had the stats_reset_on_server_start parameter and the pg_postmaster_start_time() function. This was an easy way of resetting *all* statistics delivered by pg_stat_* and knowing when this was done. We were able to produce stats with information about sec/hours/days average values in an easy way.
With this new feature I'm submitting, you can adjust your database startup scripts to make this happen again. Start the server, immediately loop over every database and call pg_stat_reset on them all, and call pg_stat_reset_shared('bgwriter'). Now you've got completely cleared stats that are within a second or two of pg_postmaster_start_time(), should be close enough to most purposes. Theoretically we could automate that better, but I've found it hard to justify working on given that it's not that difficult to handle outside of the database once the individual pieces are exposed.
-- Greg Smith 2ndQuadrant Baltimore, MD PostgreSQL Training, Services and Support g...@2ndquadrant.com www.2ndQuadrant.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
