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Faster PageIsVerified() for the all zeroes case.

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That's primarily useful for testing very large relations, using sparse
files.

Discussion: <20140331101001.GE13135@alap3.anarazel.de>
Reviewed-By: Peter Geoghegan
This commit is contained in:
Andres Freund 2016-09-08 17:02:43 -07:00
parent 769fd9d8e0
commit 417fefaf08
1 changed files with 11 additions and 4 deletions
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15
src/backend/storage/page/bufpage.c
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@ -81,7 +81,7 @@ bool
PageIsVerified(Page page, BlockNumber blkno)
{
PageHeader p = (PageHeader) page;
char *pagebytes;
size_t *pagebytes;
int i;
bool checksum_failure = false;
bool header_sane = false;
@ -118,10 +118,17 @@ PageIsVerified(Page page, BlockNumber blkno)
return true;
}
/* Check all-zeroes case */
/*
* Check all-zeroes case. Luckily BLCKSZ is guaranteed to always be a
* multiple of size_t - and it's much faster to compare memory using the
* native word size.
*/
StaticAssertStmt(BLCKSZ == (BLCKSZ / sizeof(size_t)) * sizeof(size_t),
"BLCKSZ has to be a multiple of sizeof(size_t)");
all_zeroes = true;
pagebytes = (char *) page;
for (i = 0; i < BLCKSZ; i++)
pagebytes = (size_t *) page;
for (i = 0; i < (BLCKSZ / sizeof(size_t)); i++)
{
if (pagebytes[i] != 0)
{