Re: questions about a table's row estimates
| От | Ben Chobot |
|---|---|
| Тема | Re: questions about a table's row estimates |
| Дата | |
| Msg-id | FB23ED59-D84C-4C0C-8284-3FD9B065324A@silentmedia.com обсуждение исходный текст |
| Ответ на | Re: questions about a table's row estimates (Greg Smith <greg@2ndquadrant.com>) |
| Ответы |
Re: questions about a table's row estimates
|
| Список | pgsql-general |
On Feb 10, 2010, at 10:28 PM, Greg Smith wrote:
Ben Chobot wrote:I'm looking at pg_stat_user_tables in 8.4.2, and I'm confused about n_live_tup. Shouldn't that be at least fairly close to (n_tup_ins - n_tup-del)? It doesn't seem to be, but I'm unclear why.Insert 2000 tuples.
Delete 1000 tuples.
vacuum
Insert 1000 tuples. These go into the free space the deleted tuples used to be in.
analyze
n_tup_ins=3000
n_tup_del=1000
n_live_tup=3000
Say what? It's not documented terrible well (http://www.postgresql.org/docs/8.4/interactive/monitoring-stats.html is the best I can find) but I thought n_live_tup was basically the number of tuples visible to a new transaction. If my assumption is wrong, that might explain things.
And unfortunately, Tom, we're not resetting stats counters. :(
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