I wanted to create a new relopt named something like autovacuum_vacuum_pagevisible_factor which would cause autovacuum to vacuum a table once less than a certain fraction of the relation's pages are marked allvisible.
I wanted some feedback on some things. 1) One issue is that pg_class.relpages and pg_class.relallvisible are themselves only updated by vacuum/analyze. In the absence of manual vacuum or analyze, this means that if the new criterion uses those field, it could only kick in after an autoanalyze has already been done, which means that autovacuum_vacuum_pagevisible_factor could not meaningfully be set lower than autovacuum_analyze_scale_factor. Should relallvisible be moved/copied from pg_class to pg_stat_all_tables, so that it is maintained by the stats collector? Or should the autovacuum worker just walk the vm of every table with a defined autovacuum_vacuum_pagevisible_factor each time it is launched to get an up-to-date count that way? 2) Should there be a guc in addition to the relopt? I can't think of a reason why I would want to set this globally, so I'm happy with just a relopt. If it were set globally, it would sure increase the cost for scanning the vm for each table once each naptime. 3) Should there be a autovacuum_vacuum_pagevisible_threshold? The other settings have both a factor and a threshold. I've never understand what the point of the threshold settings is, but presumably there is a point to them. Does that reason also apply to keeping vm tuned up? Cheers, Jeff -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
