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To support external compression of archived WAL data, add a flag bit to

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WAL records that shows whether it is safe to remove full-page images
(ie, whether or not an on-line backup was in progress when the WAL entry
was made).  Also make provision for an XLOG_NOOP record type that can be
used to fill in the extra space when decompressing the data for restore.

This is the portion of Koichi Suzuki's "full page writes" patch that
has to go into the core database.  The remainder of that work is two
external compression and decompression programs, which for the time being
will undergo separate development on pgfoundry.  Per discussion.

Also, twiddle the handling of BTREE_SPLIT records to ensure it'll be
possible to compress them (the previous coding caused essential info
to be omitted).  The other commonly-used record types seem OK already,
with the possible exception of GIN and GIST WAL records, which I don't
understand well enough to opine on.
This commit is contained in:
Tom Lane
2007-05-20 21:08:19 +00:00
parent 2f2717d14f
commit a8d539f124
6 changed files with 53 additions and 17 deletions
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23
src/backend/access/transam/xlog.c
View File

@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.268 2007/04/30 21:01:52 tgl Exp $
* $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.269 2007/05/20 21:08:19 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -783,6 +783,19 @@ begin:;
}
}
/*
* If we backed up any full blocks and online backup is not in progress,
* mark the backup blocks as removable. This allows the WAL archiver to
* know whether it is safe to compress archived WAL data by transforming
* full-block records into the non-full-block format.
*
* Note: we could just set the flag whenever !forcePageWrites, but
* defining it like this leaves the info bit free for some potential
* other use in records without any backup blocks.
*/
if ((info & XLR_BKP_BLOCK_MASK) && !Insert->forcePageWrites)
info |= XLR_BKP_REMOVABLE;
/*
* If there isn't enough space on the current XLOG page for a record
* header, advance to the next page (leaving the unused space as zeroes).
@ -5868,6 +5881,10 @@ xlog_redo(XLogRecPtr lsn, XLogRecord *record)
RecoveryRestartPoint(&checkPoint);
}
else if (info == XLOG_NOOP)
{
/* nothing to do here */
}
else if (info == XLOG_SWITCH)
{
/* nothing to do here */
@ -5894,6 +5911,10 @@ xlog_desc(StringInfo buf, uint8 xl_info, char *rec)
checkpoint->nextMultiOffset,
(info == XLOG_CHECKPOINT_SHUTDOWN) ? "shutdown" : "online");
}
else if (info == XLOG_NOOP)
{
appendStringInfo(buf, "xlog no-op");
}
else if (info == XLOG_NEXTOID)
{
Oid nextOid;