On Thu, Mar 04, 2021 at 12:21:14PM +0900, Fujii Masao wrote: > > > On 2021/03/04 11:24, Julien Rouhaud wrote: > > On Thu, Mar 04, 2021 at 10:35:19AM +0900, Masahiko Sawada wrote: > > > > > > While reviewing "autoanalyze on partitioned table" patch, I realized > > > that pg_stat_xxx_tables.n_mod_since_analyze is not reset at TRUNCATE. > > > On the other hand, n_ins_since_vacuum is reset. I think it should be > > > reset because otherwise we end up unnecessarily triggering autoanalyze > > > even when the actual number of newly inserted tuples is less than the > > > autoanalyze thresholds. > > In that case, conversely, we want to trigger autoanalyze ASAP because the > contents in the table was changed very much?
We might want, but wouldn't keeping the current n_mod_since_analyze would make things unpredictable? Also the selectivity estimation functions already take into account the actual relation size, so the estimates aren't completely off after a truncate.
