On Mon, Feb 22, 2021 at 4:21 AM Masahiko Sawada <sawada.m...@gmail.com> wrote: > The 0001 patch looks good to me. In the documentation, I think we need > to update the following paragraph in the description of > vacuum_cleanup_index_scale_factor:
Good point. I think that the structure should make the page deletion triggering condition have only secondary importance -- it is only described at all to be complete and exhaustive. The vacuum_cleanup_index_scale_factor-related threshold is all that users will really care about in this area. The reasons for this are: it's pretty rare to have many page deletions, but never again delete/non-hot update even one single tuple. But when that happens, it's *much* rarer still to *also* have inserts, that might actually benefit from recycling the deleted page. So it's very narrow. I think that I'll add a "Note" box that talks about the page deletion stuff, right at the end. It's actually kind of an awkward thing to describe, and yet I think we still need to describe it. I also think that the existing documentation should clearly point out that the vacuum_cleanup_index_scale_factor only gets considered when there are no updates or deletes since the last VACUUM -- that seems like an existing problem worth fixing now. It's way too unclear that this setting only really concerns append-only tables. -- Peter Geoghegan
