Re: Add LZ4 compression in pg_dump

From: gkokolatos(at)pm(dot)me
To: Michael Paquier <michael(at)paquier(dot)xyz>
Cc: Justin Pryzby <pryzby(at)telsasoft(dot)com>, pgsql-hackers(at)lists(dot)postgresql(dot)org, Rachel Heaton <rachelmheaton(at)gmail(dot)com>
Subject: Re: Add LZ4 compression in pg_dump
Date: 2023-01-16 15:14:43
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I admit I am completely at lost as to what is expected from me anymore.

I had posted v19-0001 for a committer's consideration and v19-000{2,3} for completeness.
Please find a rebased v20 attached.

Also please let me know if I should silently step away from it and let other people lead
it. I would be glad to comply either way.


------- Original Message -------
On Monday, January 16th, 2023 at 3:54 AM, Michael Paquier <michael(at)paquier(dot)xyz> wrote:

> On Sun, Jan 15, 2023 at 07:56:25PM -0600, Justin Pryzby wrote:
> > On Mon, Jan 16, 2023 at 10:28:50AM +0900, Michael Paquier wrote:
> >
> > > The functions changed by 0001 are cfopen_write,
> > > AllocateCompressor() and ReadDataFromArchive(). Why is it a good idea
> > > to change these interfaces which basically exist to handle inputs?
> >
> > I changed to pass pg_compress_specification as a pointer, since that's
> > the usual convention for structs, as followed by the existing uses of
> > pg_compress_specification.
> Okay, but what do we gain here? It seems to me that this introduces
> the risk that a careless change in one of the internal routines if
> they change slight;ly compress_spec, hence impacting any of their
> callers? Or is that fixing an actual bug (except if I am missing your
> point, that does not seem to be the case)?
> > > Is there some benefit in changing compression_spec within the
> > > internals of these routines before going back one layer down to their
> > > callers? Changing the compression_spec on-the-fly in these internal
> > > paths could be risky, actually, no?
> >
> > I think what you're saying is that if the spec is passed as a pointer,
> > then the called functions shouldn't set spec->algorithm=something.
> Yes. HEAD makes sure of that, 0001 would not prevent that. So I am a
> bit confused in seeing how this is a benefit.
> --
> Michael

Attachment Content-Type Size
v20-0001-Prepare-pg_dump-internals-for-additional-compres.patch text/x-patch 21.9 KB

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