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Add a new subclass for MemPage.xCellSize specifically for the case of a leaf

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page in a B+Tree, that is optimized for that cases.  This gains a half million
cycles or more at the cost of less than 200 bytes of code space.

FossilOrigin-Name: 7ad829224adbec5d74ff9e5ab040eb2ad3e17fe45da7a2cf0cca770a0731401a
This commit is contained in:
drh
2022-02-23 22:56:10 +00:00
parent 009a48e0ad
commit 19ae01be13
3 changed files with 62 additions and 15 deletions
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63
src/btree.c
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@@ -1327,6 +1327,7 @@ static void btreeParseCell(
** the space used by the cell pointer.
**
** cellSizePtrNoPayload() => table internal nodes
** cellSizePtrTableLeaf() => table leaf nodes
** cellSizePtr() => all index nodes & table leaf nodes
*/
static u16 cellSizePtr(MemPage *pPage, u8 *pCell){
@@ -1352,13 +1353,6 @@ static u16 cellSizePtr(MemPage *pPage, u8 *pCell){
}while( *(pIter)>=0x80 && pIter<pEnd );
}
pIter++;
if( pPage->intKey ){
/* pIter now points at the 64-bit integer key value, a variable length
** integer. The following block moves pIter to point at the first byte
** past the end of the key value. */
pEnd = &pIter[9];
while( (*pIter++)&0x80 && pIter<pEnd );
}
testcase( nSize==pPage->maxLocal );
testcase( nSize==(u32)pPage->maxLocal+1 );
if( nSize<=pPage->maxLocal ){
@@ -1398,6 +1392,58 @@ static u16 cellSizePtrNoPayload(MemPage *pPage, u8 *pCell){
assert( debuginfo.nSize==(u16)(pIter - pCell) || CORRUPT_DB );
return (u16)(pIter - pCell);
}
static u16 cellSizePtrTableLeaf(MemPage *pPage, u8 *pCell){
u8 *pIter = pCell; /* For looping over bytes of pCell */
u8 *pEnd; /* End mark for a varint */
u32 nSize; /* Size value to return */
#ifdef SQLITE_DEBUG
/* The value returned by this function should always be the same as
** the (CellInfo.nSize) value found by doing a full parse of the
** cell. If SQLITE_DEBUG is defined, an assert() at the bottom of
** this function verifies that this invariant is not violated. */
CellInfo debuginfo;
pPage->xParseCell(pPage, pCell, &debuginfo);
#endif
nSize = *pIter;
if( nSize>=0x80 ){
pEnd = &pIter[8];
nSize &= 0x7f;
do{
nSize = (nSize<<7) | (*++pIter & 0x7f);
}while( *(pIter)>=0x80 && pIter<pEnd );
}
pIter++;
/* pIter now points at the 64-bit integer key value, a variable length
** integer. The following block moves pIter to point at the first byte
** past the end of the key value. */
if( (*pIter++)&0x80
&& (*pIter++)&0x80
&& (*pIter++)&0x80
&& (*pIter++)&0x80
&& (*pIter++)&0x80
&& (*pIter++)&0x80
&& (*pIter++)&0x80
&& (*pIter++)&0x80 ){ pIter++; }
testcase( nSize==pPage->maxLocal );
testcase( nSize==(u32)pPage->maxLocal+1 );
if( nSize<=pPage->maxLocal ){
nSize += (u32)(pIter - pCell);
if( nSize<4 ) nSize = 4;
}else{
int minLocal = pPage->minLocal;
nSize = minLocal + (nSize - minLocal) % (pPage->pBt->usableSize - 4);
testcase( nSize==pPage->maxLocal );
testcase( nSize==(u32)pPage->maxLocal+1 );
if( nSize>pPage->maxLocal ){
nSize = minLocal;
}
nSize += 4 + (u16)(pIter - pCell);
}
assert( nSize==debuginfo.nSize || CORRUPT_DB );
return (u16)nSize;
}
#ifdef SQLITE_DEBUG
@@ -1880,6 +1926,7 @@ static int decodeFlags(MemPage *pPage, int flagByte){
pPage->intKey = 1;
if( pPage->leaf ){
pPage->intKeyLeaf = 1;
pPage->xCellSize = cellSizePtrTableLeaf;
pPage->xParseCell = btreeParseCellPtr;
}else{
pPage->intKeyLeaf = 0;
@@ -9310,7 +9357,7 @@ int sqlite3BtreeDelete(BtCursor *pCur, u8 flags){
bPreserve = (flags & BTREE_SAVEPOSITION)!=0;
if( bPreserve ){
if( !pPage->leaf
|| (pPage->nFree+cellSizePtr(pPage,pCell)+2)>(int)(pBt->usableSize*2/3)
|| (pPage->nFree+pPage->xCellSize(pPage,pCell)+2)>(int)(pBt->usableSize*2/3)
|| pPage->nCell==1 /* See dbfuzz001.test for a test case */
){
/* A b-tree rebalance will be required after deleting this entry.