I'm pretty late on this, but as it seems you didn't get any answer...
2017-12-04 23:49 GMT+01:00 Don Seiler <don@xxxxxxxxx>:
On Mon, Dec 4, 2017 at 4:36 PM, Alvaro Herrera <alvherre@xxxxxxxxxxxxxxx> wrote:The optimizer stats are not lost on crash or promote actually; these are
stored in pg_statistic (not in the stats collector) and *are* part of
regular "data".
...
I think it's pretty common misunderstanding -- it's not easy to see the
boundary between pg_statistic and pg_stat_* tables.Thanks for this. I thought I remembered being corrected on this before (probably on this very list) and just came to think of it at the end of my last message.So what, exactly ARE the pg_stat_* tables?
Activity statistics, collected by the stats collector process.
Is that the data stored in the files in stats_temp_directory?
Yes.
How do they differ from pg_statistic?
Those in pg_statistic are data statistics. They're used by the planner, and collected by the ANALYZE SQL command.
I've found this blog post that seems to answer that question with a "Yes": https://blog.pgaddict.com/posts/the-two-kinds-of- stats-in-postgresql
+1
--
Guillaume.
