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Changes to the btree and pager that reduce the amount of I/O when dealing

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with the freelist.  (1) Avoid journaling pages of a table that is being
deleted.  (2) Do not read the original content of pages being pulled off
of the freelist. (CVS 3671)

FossilOrigin-Name: 2ba5be311945a4c15b6dce7c01efefb513b9a973
This commit is contained in:
drh
2007-03-04 13:15:27 +00:00
parent 8efe541f24
commit 0787db6519
5 changed files with 46 additions and 41 deletions
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13
src/pager.c
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@@ -18,7 +18,7 @@
** file simultaneously, or one process from reading the database while
** another is writing.
**
** @(#) $Id: pager.c,v 1.284 2007/03/01 00:29:14 drh Exp $
** @(#) $Id: pager.c,v 1.285 2007/03/04 13:15:28 drh Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"
@@ -2625,8 +2625,13 @@ int sqlite3pager_release_memory(int nReq){
** has to go to disk, and could also playback an old journal if necessary.
** Since _lookup() never goes to disk, it never has to deal with locks
** or journal files.
**
** If clrFlag is false, the page contents are actually read from disk.
** If clfFlag is true, it means the page is about to be erased and
** rewritten without first being read so there is no point it doing
** the disk I/O.
*/
int sqlite3pager_get(Pager *pPager, Pgno pgno, void **ppPage){
int sqlite3pager_acquire(Pager *pPager, Pgno pgno, void **ppPage, int clrFlag){
PgHdr *pPg;
int rc;
@@ -2784,7 +2789,9 @@ int sqlite3pager_get(Pager *pPager, Pgno pgno, void **ppPage){
/* Populate the page with data, either by reading from the database
** file, or by setting the entire page to zero.
*/
if( sqlite3pager_pagecount(pPager)<(int)pgno || MEMDB ){
if( sqlite3pager_pagecount(pPager)<(int)pgno || MEMDB
|| (clrFlag && !pPager->alwaysRollback)
){
memset(PGHDR_TO_DATA(pPg), 0, pPager->pageSize);
}else{
assert( MEMDB==0 );