Re: zstd compression for pg_dump

On Mon, Apr 03, 2023 at 11:26:09PM +0200, Tomas Vondra wrote:
> On 4/3/23 21:17, Justin Pryzby wrote:
> > On Sat, Apr 01, 2023 at 10:26:01PM +0200, Tomas Vondra wrote:
> >>> Feel free to mess around with threads (but I'd much rather see the patch
> >>> progress for zstd:long).
> >>
> >> OK, understood. The long mode patch is pretty simple. IIUC it does not
> >> change the format, i.e. in the worst case we could leave it for PG17
> >> too. Correct?
> >
> > Right, libzstd only has one "format", which is the same as what's used
> > by the commandline tool. zstd:long doesn't change the format of the
> > output: the library just uses a larger memory buffer to allow better
> > compression. There's no format change for zstd:workers, either.
>
> OK. I plan to do a bit more review/testing on this, and get it committed
> over the next day or two, likely including the long mode. One thing I
> noticed today is that maybe long_distance should be a bool, not int.
> Yes, ZSTD_c_enableLongDistanceMatching() accepts int, but it'd be
> cleaner to cast the value during a call and keep it bool otherwise.

Thanks for noticing. Evidently I wrote it using "int" to get the
feature working, and then later wrote the bool parsing bits but never
changed the data structure.

This also updates a few comments, indentation, removes a useless
assertion, and updates the warning about zstd:workers.

--
Justin