On Mon, Jan 13, 2020 at 2:15 PM Alvaro Herrera <alvhe...@2ndquadrant.com> wrote:
> On 2020-Jan-13, Shira Bezalel wrote: > > > Hi All, > > > > I'm testing an upgrade from Postgres 9.6.16 to 12.1 and seeing a > > significant performance gain in one specific query. This is really great, > > but I'm just looking to understand why. > > pg12 reads half the number of buffers. I bet it's because of this change: > > commit 4d0e994eed83c845a05da6e9a417b4efec67efaf > Author: Stephen Frost <sfr...@snowman.net> > AuthorDate: Tue Apr 2 12:35:32 2019 -0400 > CommitDate: Tue Apr 2 12:35:32 2019 -0400 > > Add support for partial TOAST decompression > > When asked for a slice of a TOAST entry, decompress enough to return > the > slice instead of decompressing the entire object. > > For use cases where the slice is at, or near, the beginning of the > entry, > this avoids a lot of unnecessary decompression work. > > This changes the signature of pglz_decompress() by adding a boolean to > indicate if it's ok for the call to finish before consuming all of the > source or destination buffers. > > Author: Paul Ramsey > Reviewed-By: Rafia Sabih, Darafei Praliaskouski, Regina Obe > Discussion: > https://postgr.es/m/CACowWR07EDm7Y4m2kbhN_jnys%3DBBf9A6768RyQdKm_%3DNpkcaWg%40mail.gmail.com > > -- > Álvaro Herrera https://www.2ndQuadrant.com/ > PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services > That sounds like a possibility. Thanks Alvaro. Shira
