Thread

Re: Patch: dumping tables data in multiple chunks in pg_dump

Hannu Krosing <hannuk@google.com> — 2025-11-13T18:02:43Z

I just ran a test by generating a 408GB table and then dumping it both ways

$ time pg_dump --format=directory -h 10.58.80.2 -U postgres -f
/tmp/plain.dump largedb

real    39m54.968s
user    37m21.557s
sys     2m32.422s

$ time ./pg_dump --format=directory -h 10.58.80.2 -U postgres
--huge-table-chunk-pages=131072 -j 8 -f /tmp/parallel8.dump largedb

real    5m52.965s
user    40m27.284s
sys     3m53.339s

So parallel dump with 8 workers using 1GB (128k pages) chunks runs
almost 7 times faster than the sequential dump.

this was a table that had no TOAST part. I will run some more tests
with TOASTed tables next and expect similar or better improvements.



On Wed, Nov 12, 2025 at 1:59 PM Ashutosh Bapat
<ashutosh.bapat.oss@gmail.com> wrote:
>
> Hi Hannu,
>
> On Tue, Nov 11, 2025 at 9:00 PM Hannu Krosing <hannuk@google.com> wrote:
> >
> > Attached is a patch that adds the ability to dump table data in multiple chunks.
> >
> > Looking for feedback at this point:
> >  1) what have I missed
> >  2) should I implement something to avoid single-page chunks
> >
> > The flag --huge-table-chunk-pages which tells the directory format
> > dump to dump tables where the main fork has more pages than this in
> > multiple chunks of given number of pages,
> >
> > The main use case is speeding up parallel dumps in case of one or a
> > small number of HUGE tables so parts of these can be dumped in
> > parallel.
>
> Have you measured speed up? Can you please share the numbers?
>
> --
> Best Wishes,
> Ashutosh Bapat