Re: [PING] [PATCH v2] parallel pg_restore: avoid disk seeks when jumping short distance forward

Hi Nathan, I've noticed you've set yourself as a reviewer of this patch
in the commitfest. I appreciate it, but you might want to combine it
with another simple patch [1] that speeds up the same part of
pg_restore: the initial full scan on TOC-less archives.

[1] https://commitfest.postgresql.org/patch/5817/


On Saturday 2025-06-14 00:04, Nathan Bossart wrote:
>
> On Fri, Jun 13, 2025 at 01:00:26AM +0200, Dimitrios Apostolou wrote:
>> By the way, I might have set the threshold to 1MB in my program, but
>> lowering it won't show a difference in my test case, since the lseek()s I
>> was noticing before the patch were mostly 8-16KB forward. Not sure what is
>> the defining factor for that. Maybe the compression algorithm, or how wide
>> the table is?
>
> I may have missed it, but could you share what the strace looks like with
> the patch applied?

I hope you've seen my response here, with special focus on the small
block size that both compressed and uncompressed custom format archives
have.

I have been needing to pg_restore 10TB TOC-less dumps recently, and it's
a pain to do the full scan, even with both of my patches applied.

Maybe the block size could be a command line option of pg_dump, so that
one could set it to sizes like 100MB, which sounds like a normal block
from the perspective of a 10TB gigantic dump.

Regards,
Dimitris