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Change CRCs in WAL records from 64bit to 32bit for performance reasons.

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Instead of a separate CRC on each backup block, include backup blocks
in their parent WAL record's CRC; this is important to ensure that the
backup block really goes with the WAL record, ie there was not a page
tear right at the start of the backup block.  Implement a simple form
of compression of backup blocks: drop any run of zeroes starting at
pd_lower, so as not to store the unused 'hole' that commonly exists in
PG heap and index pages.  Tweak PageRepairFragmentation and related
routines to ensure they keep the unused space zeroed, so that the above
compression method remains effective.  All per recent discussions.
This commit is contained in:
Tom Lane
2005-06-02 05:55:29 +00:00
parent c196c7ae8b
commit 21fda22ec4
11 changed files with 516 additions and 212 deletions
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9
src/backend/access/nbtree/nbtxlog.c
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@ -8,7 +8,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtxlog.c,v 1.20 2005/03/22 06:17:03 tgl Exp $
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtxlog.c,v 1.21 2005/06/02 05:55:28 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -135,6 +135,13 @@ _bt_restore_meta(Relation reln, XLogRecPtr lsn,
pageop = (BTPageOpaque) PageGetSpecialPointer(metapg);
pageop->btpo_flags = BTP_META;
/*
* Set pd_lower just past the end of the metadata. This is not
* essential but it makes the page look compressible to xlog.c.
*/
((PageHeader) metapg)->pd_lower =
((char *) md + sizeof(BTMetaPageData)) - (char *) metapg;
PageSetLSN(metapg, lsn);
PageSetTLI(metapg, ThisTimeLineID);
LockBuffer(metabuf, BUFFER_LOCK_UNLOCK);