On Mon, Mar 16, 2020 at 07:47:13AM -0500, Justin Pryzby wrote: > Normally, when someone complains about bad plan related to no index-onlyscan, > we tell them to run vacuum, and if that helps, then ALTER TABLE .. SET > (autovacuum_vacuum_scale_factor=0.005). > > If there's two thresholds (4 GUCs and 4 relopts) for autovacuum, then do we > have to help determine which one was being hit, and which relopt to set?
I don't think we came to any resolution on this. Right now, to encourage IOS, we'd tell someone to set autovacuum_vacuum_scale_factor=0.005. That wouldn't work for an insert-only table, but I've never heard back from someone that it didn't work. So with this patch, we'd maybe tell them to do this, to also get IOS on insert-only tables ? |ALTER TABLE .. SET (autovacuum_vacuum_scale_factor=0.005, autovacuum_vacuum_insert_threshold=50000); > I wonder if the new insert GUCs should default to -1 (disabled)? And the > insert thresholds should be set by new insert relopt (if set), or by new > insert > GUC (default -1), else normal relopt, or normal GUC. The defaults would give > 50 + 0.20*n. When someone asks about IOS, we'd tell them to set > autovacuum_vacuum_scale_factor=0.005, same as now. > > vac_ins_scale_factor = > (relopts && relopts->vacuum_ins_scale_factor >= 0) ? > relopts->vacuum_ins_scale_factor : > autovacuum_vac_ins_scale >= 0 ? autovacuum_vac_ins_scale : > (relopts && relopts->vacuum_scale_factor >= 0) ? > relopts->vacuum_scale_factor : > autovacuum_vac_scale; -- Justin
