On Sat, Sep 23, 2017 at 6:10 PM, Jack Christensen <j...@jackchristensen.com> wrote:
> Just had an issue where a prepared query would occasionally choose a very > bad plan in production. The same data set in a different environment > consistently would choose the index scan. As would be expected, running > analyze on that table in production resolved the issue. > > However, before I ran the analyze I checked pg_stat_user_tables to see > last_autoanalyze for that table. It had run today. But the problem existed > before that. I would have expected that the auto-analyze would have > corrected this (or prevented it entirely if run enough). > > So that leaves me wondering: is an auto-analyze the same as manually > running analyze or is a manual analyze more thorough? This is running > version 9.6.3 on Heroku. > > Thanks, > > Jack > > > > > -- > Sent via pgsql-general mailing list (pgsql-general@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-general > >is an auto-analyze the same as manually running analyze or is a manual analyze more thorough? It's not that one is "more thorough" than the other, it's that autovacuum_analyze will only kick in when it meets one of the following conditions: autovacuum_analyze_scale_factor 0.1 #Number of tuple inserts, updates, or deletes prior to analyze as a fraction of reltuples. autovacuum_analyze_threshold 50 #Minimum number of tuple inserts, updates, or deletes prior to analyze. https://www.postgresql.org/docs/9.6/static/runtime-config-autovacuum.html Note: You can adjust the settings for individual tables. EG: *ALTER TABLE some_schema.your_table SET (autovacuum_vacuum_scale_factor = 0.5); ALTER TABLE some_schema.your_table SET (autovacuum_vacuum_threshold = 1000);* -- *Melvin Davidson* I reserve the right to fantasize. Whether or not you wish to share my fantasy is entirely up to you.
