Re: [PATCHES] Full page writes improvement, code update

Hi,

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.

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As suggested by Tom, I agree that WAL should not include "both" full
page write and incremental (logical) log. I began to examine WAL
record format to see if incremental log can be made from full page
writes. It will be okay even before 8.4, if simplified patch to the
core is accepted. I will post simplified patch to the core as follows:

1. Mark the flag to indicate that the WAL record is compressable from
full page writes to incremental log. This flag will be set if
a) It is not written during the hot backup, and
b) Archive command is active, and
c) WAL contains full page writes, and
d) full_page_writes=on.
No logical log will be written to WAL in this case, and
2. During recovery, xl_tot_len check will be skipped for compressed WAL
records.

Please note that new GUC is not needed in this patch.

With this patch, compress/decompress can be developped outside the core.

I'd be very grateful if this patch can be considered again.

Best Regards;

--
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Koichi Suzuki