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Add code to apply some simple sanity checks to the header fields of a

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page when it's read in, per pghackers discussion around 17-Feb.  Add a
GUC variable zero_damaged_pages that causes the response to be a WARNING
followed by zeroing the page, rather than the normal ERROR; this is per
Hiroshi's suggestion that there needs to be a way to get at the data
in the rest of the table.
This commit is contained in:
Tom Lane
2003-03-28 20:17:13 +00:00
parent bb3c00ee28
commit fd42262836
8 changed files with 104 additions and 73 deletions
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49
src/backend/storage/page/bufpage.c
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@@ -8,14 +8,12 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/storage/page/bufpage.c,v 1.51 2003/01/11 05:01:03 momjian Exp $
* $Header: /cvsroot/pgsql/src/backend/storage/page/bufpage.c,v 1.52 2003/03/28 20:17:13 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include <sys/file.h>
#include "storage/bufpage.h"
@@ -48,6 +46,51 @@ PageInit(Page page, Size pageSize, Size specialSize)
}
/*
* PageHeaderIsValid
* Check that the header fields of a page appear valid.
*
* This is called when a page has just been read in from disk. The idea is
* to cheaply detect trashed pages before we go nuts following bogus item
* pointers, testing invalid transaction identifiers, etc.
*
* It turns out to be necessary to allow zeroed pages here too. Even though
* this routine is *not* called when deliberately adding a page to a relation,
* there are scenarios in which a zeroed page might be found in a table.
* (Example: a backend extends a relation, then crashes before it can write
* any WAL entry about the new page. The kernel will already have the
* zeroed page in the file, and it will stay that way after restart.) So we
* allow zeroed pages here, and are careful that the page access macros
* treat such a page as empty and without free space. Eventually, VACUUM
* will clean up such a page and make it usable.
*/
bool
PageHeaderIsValid(PageHeader page)
{
char *pagebytes;
int i;
/* Check normal case */
if (PageGetPageSize(page) == BLCKSZ &&
PageGetPageLayoutVersion(page) == PG_PAGE_LAYOUT_VERSION &&
page->pd_lower >= SizeOfPageHeaderData &&
page->pd_lower <= page->pd_upper &&
page->pd_upper <= page->pd_special &&
page->pd_special <= BLCKSZ &&
page->pd_special == MAXALIGN(page->pd_special))
return true;
/* Check all-zeroes case */
pagebytes = (char *) page;
for (i = 0; i < BLCKSZ; i++)
{
if (pagebytes[i] != 0)
return false;
}
return true;
}
/* ----------------
* PageAddItem
*