On Mon, Jan 30, 2023 at 6:30 PM Nathan Bossart <nathandboss...@gmail.com> wrote: > My colleague Jeremy Schneider (CC'd) was recently looking into usage count > distributions for various workloads, and he mentioned that it would be nice > to have an easy way to do $SUBJECT. I've attached a patch that adds a > pg_buffercache_usage_counts() function. This function returns a row per > possible usage count with some basic information about the corresponding > buffers. > > postgres=# SELECT * FROM pg_buffercache_usage_counts(); > usage_count | buffers | dirty | pinned > -------------+---------+-------+-------- > 0 | 0 | 0 | 0 > 1 | 1436 | 671 | 0 > 2 | 102 | 88 | 0 > 3 | 23 | 21 | 0 > 4 | 9 | 7 | 0 > 5 | 164 | 106 | 0 > (6 rows) > > This new function provides essentially the same information as > pg_buffercache_summary(), but pg_buffercache_summary() only shows the > average usage count for the buffers in use. If there is interest in this > idea, another approach to consider could be to alter > pg_buffercache_summary() instead.
I'm skeptical that pg_buffercache_summary() is a good idea at all, but having it display the average usage count seems like a particularly poor idea. That information is almost meaningless. Replacing that with a six-element integer array would be a clear improvement and, IMHO, better than adding yet another function to the extension. -- Robert Haas EDB: http://www.enterprisedb.com
