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In function moveToRoot(), use the MemPage.pParent pointers to find the root page if they are valid. This is slightly faster than requesting a new reference to the root page from the pager layer. (CVS 5725)

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FossilOrigin-Name: 0c8b74e668b7462c5439c04993d1d7cd74210075
This commit is contained in:
danielk1977
2008-09-19 16:39:38 +00:00
parent ea89730823
commit d9f6c53232
3 changed files with 38 additions and 13 deletions
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37
src/btree.c
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@@ -9,7 +9,7 @@
** May you share freely, never taking more than you give.
**
*************************************************************************
** $Id: btree.c,v 1.515 2008/09/19 15:10:58 danielk1977 Exp $
** $Id: btree.c,v 1.516 2008/09/19 16:39:38 danielk1977 Exp $
**
** This file implements a external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
@@ -3564,8 +3564,22 @@ static int moveToRoot(BtCursor *pCur){
clearCursorPosition(pCur);
}
pRoot = pCur->pPage;
if( pRoot && pRoot->pgno==pCur->pgnoRoot ){
if( pRoot && pRoot->isInit ){
/* If the page the cursor is currently pointing to is fully initialized,
** then the root page can be found by following the MemPage.pParent
** pointers. This is faster than requesting a reference to the root
** page from the pager layer.
*/
while( pRoot->pParent ){
assert( pRoot->isInit==PAGE_ISINIT_FULL );
pRoot = pRoot->pParent;
}
assert( pRoot->isInit==PAGE_ISINIT_FULL );
if( pRoot!=pCur->pPage ){
sqlite3PagerRef(pRoot->pDbPage);
releasePage(pCur->pPage);
pCur->pPage = pRoot;
}
}else{
if(
SQLITE_OK!=(rc = getAndInitPage(pBt, pCur->pgnoRoot, &pRoot, 0))
@@ -3576,6 +3590,7 @@ static int moveToRoot(BtCursor *pCur){
releasePage(pCur->pPage);
pCur->pPage = pRoot;
}
assert( pCur->pPage->pgno==pCur->pgnoRoot );
pCur->idx = 0;
pCur->info.nSize = 0;
pCur->atLast = 0;
@@ -3745,7 +3760,6 @@ int sqlite3BtreeMovetoUnpacked(
}
}
rc = moveToRoot(pCur);
if( rc ){
return rc;
@@ -6472,18 +6486,29 @@ int sqlite3BtreeGetMeta(Btree *p, int idx, u32 *pMeta){
}
assert( idx>=0 && idx<=15 );
if( !pBt->pPage1 ){
if( pBt->pPage1 ){
/* The b-tree is already holding a reference to page 1 of the database
** file. In this case the required meta-data value can be read directly
** from the page data of this reference. This is slightly faster than
** requesting a new reference from the pager layer.
*/
pP1 = (unsigned char *)pBt->pPage1->aData;
}else{
/* The b-tree does not have a reference to page 1 of the database file.
** Obtain one from the pager layer.
*/
rc = sqlite3PagerGet(pBt->pPager, 1, &pDbPage);
if( rc ){
sqlite3BtreeLeave(p);
return rc;
}
pP1 = (unsigned char *)sqlite3PagerGetData(pDbPage);
}else{
pP1 = (unsigned char *)pBt->pPage1->aData;
}
*pMeta = get4byte(&pP1[36 + idx*4]);
/* If the b-tree is not holding a reference to page 1, then one was
** requested from the pager layer in the above block. Release it now.
*/
if( !pBt->pPage1 ){
sqlite3PagerUnref(pDbPage);
}