At Mon, 19 Sep 2022 18:46:17 +0530, Bharath Rupireddy <bharath.rupireddyforpostg...@gmail.com> wrote in > walsener.c might work, but that didn't help either. Can anyone please > let me know why the stats that I added aren't shown via pg_stat_wal > view despite the walsender doing pgstat_initialize() -> > pgstat_init_wal()? Am I missing something? > > I'm attaching here with the patch that I was using.
pgstat_report_wal() is supposed to be called on user-facing (or query executing) backends. The function is called while in idle state on such backends. Other processes need to call one or more friend functions as needed. Checkpointer calls pgstat_report_checkpoint/wal() at the end of an iteration of the main waiting loop. Walwriter does the same with pgstat_report_wal(). Thus we need to do the same on startup process somewhere within the redo loop but where that call doesn't cause contention on shared stats area. About what the patch does, it increments the xlogreader_cache_hits counter when the WAL page to read have been already loaded, but it's not a cache but a buffer. The counter would approximately shows the number about mean-(raw)-records-per-wal-page * wal-page-ever-read. (mean-records-per-wal-page = page-size / mean-record-length). So I don't think that the value offers something valuable. I guess that the same value (for the moment) can be calculated from the result of pg_get_wal_records_info(). regards. -- Kyotaro Horiguchi NTT Open Source Software Center
