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Add the SQLITE_IOCAP_BYPASS device characteristic. Do not allow the

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SQLITE_DIRECT_OVERFLOW_READ optimization if that capability is missing.

FossilOrigin-Name: f50ae00ce9ff572e6bd5e2788602ba356383526ab7289622a32fbf52926c6df0
This commit is contained in:
drh
2024-10-22 18:00:26 +00:00
parent 76e48f4d66
commit c8284c766a
6 changed files with 36 additions and 17 deletions
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20
src/pager.c
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@@ -808,18 +808,26 @@ static const unsigned char aJournalMagic[] = {
** Return true if page pgno can be read directly from the database file
** by the b-tree layer. This is the case if:
**
** * the database file is open,
** * there are no dirty pages in the cache, and
** * the desired page is not currently in the wal file.
** (1) the database file is open
** (2) the VFS for the database has BYPASS capability
** (3) there are no dirty pages in the cache, and
** (4) the desired page is not currently in the wal file.
*/
int sqlite3PagerDirectReadOk(Pager *pPager, Pgno pgno){
if( pPager->fd->pMethods==0 ) return 0;
if( sqlite3PCacheIsDirty(pPager->pPCache) ) return 0;
assert( pPager!=0 );
assert( pPager->fd!=0 );
if( pPager->fd->pMethods==0 ) return 0; /* Case (1) */
assert( pPager->fd->pMethods->xDeviceCharacteristics!=0 );
if( (pPager->fd->pMethods->xDeviceCharacteristics(pPager->fd)
& SQLITE_IOCAP_BYPASS)==0 ){
return 0; /* Case (2) */
}
if( sqlite3PCacheIsDirty(pPager->pPCache) ) return 0; /* Failed (3) */
#ifndef SQLITE_OMIT_WAL
if( pPager->pWal ){
u32 iRead = 0;
(void)sqlite3WalFindFrame(pPager->pWal, pgno, &iRead);
return iRead==0;
return iRead==0; /* Condition (4) */
}
#endif
return 1;