Re: Different compression methods for FPI

From: Justin Pryzby <pryzby(at)telsasoft(dot)com>
To: Andrey Borodin <x4mmm(at)yandex-team(dot)ru>
Cc: Michael Paquier <michael(at)paquier(dot)xyz>, pgsql-hackers(at)postgresql(dot)org, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>
Subject: Re: Different compression methods for FPI
Date: 2021-03-21 19:30:04
Message-ID: 20210321193004.GA4203@telsasoft.com
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rebased to keep cfbot happy. This will run with default=zlib.

On Mon, Mar 15, 2021 at 01:09:18PM -0500, Justin Pryzby wrote:
> On Sun, Mar 14, 2021 at 07:31:35PM -0500, Justin Pryzby wrote:
> > On Sat, Mar 13, 2021 at 08:48:33PM +0500, Andrey Borodin wrote:
> > > > 13 марта 2021 г., в 06:28, Justin Pryzby <pryzby(at)telsasoft(dot)com> написал(а):
> > > > Updated patch with a minor fix to configure.ac to avoid warnings on OSX.
> > > > And 2ndary patches from another thread to allow passing recovery tests.
> > > > Renamed to WAL_COMPRESSION_*
> > > > Split LZ4 support to a separate patch and support zstd. These show that
> > > > changes needed for a new compression method have been minimized, although not
> > > > yet moved to a separate, abstracted compression/decompression function.
> > >
> > > Thanks! Awesome work!
> > >
> > > > These two patches are a prerequisite for this patch to progress:
> > > > * Run 011_crash_recovery.pl with wal_level=minimal
> > > > * Make sure published XIDs are persistent
> > > >
> > > > I don't know if anyone will consider this patch for v14 - if not, it should be
> > > > set to v15 and revisit in a month.
> > >
> > > I want to note, that fixes for 011_crash_recovery.pl are not strictly necessary for this patch set.
> > > The problem in tests arises if we turn on wal_compression, absolutely independently from wal compression method.
> > > We turn on wal_compression in this test only for CI purposes.
> >
> > I rearranged the patches to reflect this.
> > Change to zlib and zstd to level=1.
> > Add support for negative "zstd fast" levels.
> > Use correct length accounting for "hole" in LZ4 and ZSTD.
> > Fixed Solution.pm for zstd on windows.
> > Switch to zstd by default (for CI).
> > Add docs.
>
> Changes:
> - Allocate buffer sufficient to accommodate any supported compression method;
> - Use existing info flags argument rather than adding another byte for storing
> the compression method; this seems to be what was anticipated by commit
> 57aa5b2bb and what Michael objected to.
>
> I think the existing structures are ugly, so maybe this suggests using a GUC
> assign hook to support arbitrary compression level, and maybe other options.

Attachment Content-Type Size
0001-Allow-alternate-compression-methods-for-wal_compress.patch text/x-diff 15.0 KB
0002-Run-011_crash_recovery.pl-with-wal_level-minimal.patch text/x-diff 1001 bytes
0003-Make-sure-published-XIDs-are-persistent.patch text/x-diff 7.2 KB
0004-wal_compression_method-default-to-zlib.patch text/x-diff 1.5 KB
0005-re-add-wal_compression_method-lz4.patch text/x-diff 5.1 KB
0006-add-wal_compression_method-zstd.patch text/x-diff 13.6 KB

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