From: | "Koichi Suzuki" <koichi(dot)szk(at)gmail(dot)com> |
---|---|
To: | "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | "Koichi Suzuki" <suzuki(dot)koichi(at)oss(dot)ntt(dot)co(dot)jp>, "Josh Berkus" <josh(at)agliodbs(dot)com>, "Zeugswetter Andreas ADI SD" <ZeugswetterA(at)spardat(dot)at>, pgsql-hackers(at)postgresql(dot)org, pgsql-patches(at)postgresql(dot)org |
Subject: | Re: [PATCHES] Full page writes improvement, code update |
Date: | 2007-05-22 05:20:15 |
Message-ID: | a778a7260705212220n4df34585me1c44eb3d43eb857@mail.gmail.com |
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Lists: | pgsql-hackers pgsql-patches |
I really appreciate for the modification.
I also believe XLOG_NOOP is cool to maintains XLOG format consistent.
I'll continue to write a code to produce incremental log record from
the full page writes as well as too maintain CRC, XLOOG_NOOP and
other XLOG locations, I also found that you've added information on
btree strip log records, which anables to produce corresponding
incremental logs from the full page writes.
2007/5/21, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:
> Koichi Suzuki <suzuki(dot)koichi(at)oss(dot)ntt(dot)co(dot)jp> writes:
> > As replied to "Patch queue triage" by Tom, here's simplified patch to
> > mark WAL record as "compressable", with no increase in WAL itself.
> > Compression/decompression commands will be posted separately to PG
> > Foundary for further review.
>
> Applied with some minor modifications. I didn't like the idea of
> suppressing the sanity-check on WAL record length; I think that's
> fairly important. Instead, I added a provision for an XLOG_NOOP
> WAL record type that can be used to fill in the extra space.
> The way I envision that working is that the compressor removes
> backup blocks and converts each compressible WAL record to have the
> same contents and length it would've had if written without backup
> blocks. Then, it inserts an XLOG_NOOP record with length set to
> indicate the amount of extra space that needs to be chewed up --
> but in the compressed version of the WAL file, XLOG_NOOP's "data
> area" is not actually stored. The decompressor need only scan
> the file looking for XLOG_NOOP and insert the requisite number of
> zero bytes (and maybe recompute the XLOG_NOOP's CRC, depending on
> whether you want it to be valid for the short-format record in the
> compressed file). There will also be some games to be played for
> WAL page boundaries, but you had to do that anyway.
>
> regards, tom lane
>
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--
------
Koichi Suzuki
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