On Mon, May 10, 2021 at 04:14:56PM -0700, Peter Geoghegan wrote: > 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.
Agreed, that is a very interesting distinction. > 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. OK, once I dug into what you two were saying, I see the significance. I was frankly surprised we didn't already have these optimizations, and you are right they can lead to long-term problems. -- Bruce Momjian <br...@momjian.us> https://momjian.us EDB https://enterprisedb.com If only the physical world exists, free will is an illusion.
