Re: Experimenting with hash tables inside pg_dump

Hi,

On 2021-10-21 20:22:56 -0400, Tom Lane wrote:
> Andres Freund <andres@anarazel.de> writes:
> Yeah, that.  I tried doing a system-wide "perf" measurement, and soon
> realized that a big fraction of the time for a "pg_dump -s" run is
> being spent in the planner :-(.

A trick for seeing the proportions of this easily in perf is to start both
postgres and pg_dump pinned to a specific CPU, and profile that cpu. That gets
rid of most of the noise of other programs etc.



> I'm currently experimenting with
> PREPARE'ing pg_dump's repetitive queries, and it's looking very
> promising.  More later.

Good idea.

I wonder though if for some of them we should instead replace the per-object
queries with one query returning the information for all objects of a type. It
doesn't make all that much sense that we build and send one query for each
table and index.

Greetings,

Andres Freund