Re: Can we get rid of repeated queries from pg_dump?

On Mon, Aug 30, 2021 at 08:11:00PM -0400, Tom Lane wrote:
> [ redirecting to -hackers ]
>
> I wrote:
> > I experimented with the attached, very quick-n-dirty patch to collect
> > format_type results during the initial scan of pg_type, instead. On the
> > regression database in HEAD, it reduces the number of queries pg_dump
> > issues from 3260 to 2905; but I'm having a hard time detecting any net
> > performance change.
>
> I decided that that patch wasn't too safe, because it applies
> format_type() to pg_type rows that we have no reason to trust the
> longevity of. I think it could fall over if some concurrent process
> were busy dropping a temp table, for example.
>
> So here's a version that just does plain caching of the results
> of retail getFormattedTypeName() calls. This visibly adds no
> queries that were not done before, so it should be safe enough.
> And there can't be any cases that it makes slower, either.

Hi,
tested it in my case, and it reduced query count to 4261.

Which is great.

But, I also looked closer into the pg_proc queries and extensions.
And - most functions come from relatively standard extensions:
- postgis 1246 functions
- btree_gist 179 functions
- btree_gin 87 functions
- hstore 58 functions

My point in here is that potential optimizations regarding queries for
pg_proc might speed up dumps for more people - as they might use things
like postgis, but never realized that it can be much faster.

Best regards,

depesz