On Wed, 1 Nov 2023 at 07:47, Pavel Stehule <pavel.steh...@gmail.com> wrote: > > Hi > > út 31. 10. 2023 v 22:12 odesílatel Matthias van de Meent > <boekewurm+postg...@gmail.com> napsal: >> This patch was originally suggested at [0], but it was mentioned that >> they could be pulled out into it's own thread. Earlier, the >> performance gains were not clearly there for just this patch, but >> after further benchmarking this patch stands on its own for >> performance: it sees no obvious degradation of performance, while >> gaining 0-5% across various normal indexes on the cc-complete sample >> dataset, with the current worst-case index shape getting a 60%+ >> improved performance on INSERTs in the tests at [0]. > > > +1
Thanks for showing interest. > This can be nice functionality. I had a customer with a very slow index scan > - the main problem was a long common prefix like prg010203xxxx. I'll have to note that this patch doesn't cover cases where e.g. text attributes have large shared prefixes, but are still unique: the dynamic prefix compression in this patch is only implemented at the tuple attribute level; it doesn't implement type aware dynamic prefix compression inside the attributes. So, a unique index on a column of int32 formatted like '%0100i' would not materially benefit from this patch. While would certainly be possible to add some type-level prefix truncation in the framework of this patch, adding that would require significant code churn in btree compare operators, because we'd need an additional return argument to contain a numerical "shared prefix", and that is not something I was planning to implement in this patch. Kind regards, Matthias van de Meent Neon (https://neon.tech)
