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Add SQLITE_IOCAP_ZERO_DAMAGE and enable it for both unix and windows. Use

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this device characteristic to reduce the required work in journaling.
A side effect is that this changes the default page exists back to 1024
even with the use of statvfs().

FossilOrigin-Name: a0be6ea464695fdf1eaf2b7cf0652778617814f2
This commit is contained in:
drh
2011-12-17 19:49:02 +00:00
parent 9c0e29371e
commit 8bbaa89d8d
9 changed files with 65 additions and 40 deletions
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13
src/pager.c
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@@ -2515,11 +2515,22 @@ static int pager_truncate(Pager *pPager, Pgno nPage){
** the value returned by the xSectorSize() method rounded up to 32 if
** it is less than 32, or rounded down to MAX_SECTOR_SIZE if it
** is greater than MAX_SECTOR_SIZE.
**
** If the file has the SQLITE_IOCAP_ZERO_DAMAGE property, then set the
** effective sector size to its minimum value (512). The purpose of
** pPager->sectorSize is to define the "blast radius" of bytes that
** might change if a crash occurs while writing to a single byte in
** that range. But with ZERO_DAMAGE, the blast radius is zero, so
** we minimize the sector size. For backwards compatibility of the
** rollback journal file format, we cannot reduce the effective sector
** size below 512.
*/
static void setSectorSize(Pager *pPager){
assert( isOpen(pPager->fd) || pPager->tempFile );
if( !pPager->tempFile ){
if( !pPager->tempFile
&& (sqlite3OsDeviceCharacteristics(pPager->fd)&SQLITE_IOCAP_ZERO_DAMAGE)==0
){
/* Sector size doesn't matter for temporary files. Also, the file
** may not have been opened yet, in which case the OsSectorSize()
** call will segfault.