On Mon, May 10, 2021 at 3:58 PM Bruce Momjian <br...@momjian.us> wrote: > OK, you are confirming what Matthias suggested. I added these two > items, which both seem to apply only to heap pages, not index pages:
That's right -- these two relate to heap pages only. I think that Matthias compared these two to bottom-up index deletion because all three patches are concerned about avoiding "a permanent solution to a temporary problem". They're conceptually similar despite being in fairly different areas. Evidently Matthias has a similar mental model to my own when it comes to this stuff. Unfortunately the practical significance of the line pointer patch is hard to demonstrate with a benchmark. I believe that it is very useful on a sufficiently long timeline and with certain workloads because of the behavior it avoids. As I pointed out on that other thread recently, once you have irreversible bloat very small adverse events will eventually add up and cause big problems. When this happens it'll be very hard or impossible to detect, since it just looks like heap fragmentation. That said, it's clearly an issue with one of the TPC-C tables if you run BenchmarkSQL for days and days (just one table, though). So there is hard evidence that line pointer bloat could get really out of hand in at least some tables. -- Peter Geoghegan
