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During WAL recovery, when reading a page that we intend to overwrite completely

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from the WAL data, don't bother to physically read it; just have bufmgr.c
return a zeroed-out buffer instead.  This speeds recovery significantly,
and also avoids unnecessary failures when a page-to-be-overwritten has corrupt
page headers on disk.  This replaces a former kluge that accomplished the
latter by pretending zero_damaged_pages was always ON during WAL recovery;
which was OK when the kluge was put in, but is unsafe when restoring a WAL
log that was written with full_page_writes off.

Heikki Linnakangas
This commit is contained in:
Tom Lane
2007-05-02 23:18:03 +00:00
parent 8ec943856a
commit 8c3cc86e7b
3 changed files with 49 additions and 13 deletions
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3
src/include/storage/bufmgr.h
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@@ -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/include/storage/bufmgr.h,v 1.102 2007/01/05 22:19:57 momjian Exp $
* $PostgreSQL: pgsql/src/include/storage/bufmgr.h,v 1.103 2007/05/02 23:18:03 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -111,6 +111,7 @@ extern DLLIMPORT int32 *LocalRefCount;
* prototypes for functions in bufmgr.c
*/
extern Buffer ReadBuffer(Relation reln, BlockNumber blockNum);
extern Buffer ReadOrZeroBuffer(Relation reln, BlockNumber blockNum);
extern void ReleaseBuffer(Buffer buffer);
extern void UnlockReleaseBuffer(Buffer buffer);
extern void MarkBufferDirty(Buffer buffer);