пт, 6 мар. 2020 г. в 20:14, Julien Rouhaud <rjuju...@gmail.com>: > > On Thu, Mar 5, 2020 at 8:55 PM Kirill Bychik <kirill.byc...@gmail.com> wrote: > > > > > While at it, did you consider adding a full-page image counter in the > > > WalUsage? > > > That's something I'd really like to have and it doesn't seem hard to > > > integrate. > > > > Well, not sure I understand you 100%, being new to Postgres dev. Do > > you want a separate counter for pages written whenever doPageWrites is > > true? I can do that, if needed. Please confirm. > > Yes, I meant a separate 3rd counter for the number of full page images > written. However after a quick look I think that a FPI should be > detected with (doPageWrites && fpw_lsn != InvalidXLogRecPtr && fpw_lsn > <= RedoRecPtr).
This seems easy, will implement once I get some spare time. > > > Another point is that this patch won't help to see autovacuum activity. > > > As an example, I did a quick te..... > > > ...LONG QUOTE... > > > but that may seem strange to only account for (auto)vacuum activity, > > > rather > > > than globally, grouping per RmgrId or CommandTag for instance. We could > > > then > > > see the complete WAL usage per-database. What do you think? > > > > I wanted to keep the patch small and simple, and fit to practical > > needs. This patch is supposed to provide tuning assistance, catching > > an io heavy query in commit-bound situation. > > Total WAL usage per DB can be assessed rather easily using other means. > > Let's get this change into the codebase and then work on connecting > > WAL usage to (auto)vacuum stats. > > I agree that having a view of the full activity is a way bigger scope, > so it could be done later (and at this point in pg14), but I'm still > hoping that we can get insight of other backend WAL activity, such as > autovacuum, in pg13. How do you think this information should be exposed? Via the pg_stat_statement? Anyways, I believe this change could be bigger than FPI. I propose to plan a separate patch for it, or even add it to the TODO after the core patch of wal usage is merged. Please expect a new patch version next week, with FPI counters added.
