Re: Reducing relcache memory usage: deduping index shapes

On Wed, 2 Sept 2026 at 10:09, David Geier <geidav(dot)pg(at)gmail(dot)com> wrote:
>
> >> Can you provide information about how much memory is being saved from 0004+0005?
> >
> > Attached the output for a query on catcache/relcache memory context
> > data, with output of master and the full patchset.
> >
> > From Master to 0003, we go from 287872 bytes total to 141312 bytes
> > total spent on "index info" contexts (some of which moved into other
> > contexts, some new, but a net saving of 130kB). 0004+0005 bring that
> > down all the way to 45392 bytes; most of which is just avoiding the
> > large overhead of the pre-allocated Blocks of memory, saving another
> > 95kB.
> Did you just startup the server and run that query or did you run some
> something first to populate the relcache?

I ran both "\d+ pg_catalog.*" and "\di+ pg_catalog.*" in the session
before running the query, so it should be a representative sample of
all indexes in a freshly initdb'ed system.

> Maybe I'm missing something but in my understanding the relcache is
> populated as relations are accessed.

Correct.

Kind regards,

Matthias van de Meent
Databricks (https://www.databricks.com)