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Modify the assemblePage() function in btree.c so that it runs slightly faster. (CVS 6569)

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FossilOrigin-Name: 7ec42e989f1d4abdc6d52f8feebf51985f36b2bd
This commit is contained in:
danielk1977
2009-04-29 17:49:59 +00:00
parent d9c20d71c2
commit fad9194453
3 changed files with 32 additions and 40 deletions
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56
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 1.598 2009/04/29 11:31:47 danielk1977 Exp $
** $Id: btree.c,v 1.599 2009/04/29 17:49:59 danielk1977 Exp $
**
** This file implements a external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
@@ -961,13 +961,13 @@ static int allocateSpace(MemPage *pPage, int nByte){
if( size>=nByte ){
int x = size - nByte;
if( x<4 ){
/* Remove the slot from the free-list. Update the number of
** fragmented bytes within the page. */
/* Remove the slot from the free-list. Update the number of
** fragmented bytes within the page. */
memcpy(&data[addr], &data[pc], 2);
data[hdr+7] = (u8)(nFrag + x);
}else{
/* The slot remains on the free-list. Reduce its size to account
** for the portion used by the new allocation. */
/* The slot remains on the free-list. Reduce its size to account
** for the portion used by the new allocation. */
put2byte(&data[pc+2], x);
}
return pc + x;
@@ -3912,7 +3912,6 @@ int sqlite3BtreeLast(BtCursor *pCur, int *pRes){
assert( pCur->eState==CURSOR_VALID );
*pRes = 0;
rc = moveToRightmost(pCur);
getCellInfo(pCur);
pCur->atLast = rc==SQLITE_OK ?1:0;
}
}
@@ -5044,39 +5043,32 @@ static void assemblePage(
u16 *aSize /* Sizes of the cells */
){
int i; /* Loop counter */
int totalSize; /* Total size of all cells */
int hdr; /* Index of page header */
int cellptr; /* Address of next cell pointer */
u8 *pCellptr; /* Address of next cell pointer */
int cellbody; /* Address of next cell body */
u8 *data; /* Data for the page */
u8 * const data = pPage->aData; /* Pointer to data for pPage */
const int hdr = pPage->hdrOffset; /* Offset of header on pPage */
const int nUsable = pPage->pBt->usableSize; /* Usable size of page */
assert( pPage->nOverflow==0 );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
assert( nCell>=0 && nCell<=MX_CELL(pPage->pBt) && MX_CELL(pPage->pBt)<=5460 );
totalSize = 0;
for(i=0; i<nCell; i++){
totalSize += aSize[i];
}
assert( totalSize+2*nCell<=pPage->nFree );
assert( pPage->nCell==0 );
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
cellptr = pPage->cellOffset;
data = pPage->aData;
hdr = pPage->hdrOffset;
put2byte(&data[hdr+3], nCell);
if( nCell ){
cellbody = allocateSpace(pPage, totalSize);
assert( cellbody>0 );
assert( pPage->nFree >= 2*nCell );
pPage->nFree -= 2*nCell;
for(i=0; i<nCell; i++){
put2byte(&data[cellptr], cellbody);
memcpy(&data[cellbody], apCell[i], aSize[i]);
cellptr += 2;
cellbody += aSize[i];
}
assert( cellbody==pPage->pBt->usableSize );
/* Check that the page has just been zeroed by zeroPage() */
assert( pPage->nCell==0 );
assert( get2byte(&data[hdr+5])==nUsable );
pCellptr = &data[pPage->cellOffset + nCell*2];
cellbody = nUsable;
for(i=nCell-1; i>=0; i--){
pCellptr -= 2;
cellbody -= aSize[i];
put2byte(pCellptr, cellbody);
memcpy(&data[cellbody], apCell[i], aSize[i]);
}
put2byte(&data[hdr+3], nCell);
put2byte(&data[hdr+5], cellbody);
pPage->nFree -= (nCell*2 + nUsable - cellbody);
pPage->nCell = (u16)nCell;
}