On Fri, Mar 2, 2018 at 10:53 AM, Masahiko Sawada <sawada.m...@gmail.com> wrote:
> > 2) In the append-only case, index statistics can lag indefinitely. > > The original proposal proposed a new GUC that specifies a fraction of > the modified pages to trigger a cleanup indexes. Regarding original proposal, I didn't get what exactly it's intended to be. You're checking if vacuumed_pages >= nblocks * vacuum_cleanup_index_scale. But vacuumed_pages is the variable which could be incremented when no indexes exist on the table. When indexes are present, this variable is always zero. I can assume, that it's intended to compare number of pages where at least one tuple is deleted to nblocks * vacuum_cleanup_index_scale. But that is also not an option for us, because we're going to optimize the case when exactly zero tuples is deleted by vacuum. The thing I'm going to propose is to add estimated number of tuples in table to IndexVacuumInfo. Then B-tree can memorize that number of tuples when last time index was scanned in the meta-page. If pass value is differs from the value in meta-page too much, then cleanup is forced. Any better ideas? ------ Alexander Korotkov Postgres Professional: http://www.postgrespro.com The Russian Postgres Company
