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Avoid parsing cells that fit entirely on the b-tree page when searching a b-tree index. (CVS 6601)

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FossilOrigin-Name: 77a8239548722f702ead9d7c60df0d68180948fb
This commit is contained in:
danielk1977
2009-05-04 19:01:26 +00:00
parent eba661f88f
commit 11c327aabe
3 changed files with 47 additions and 25 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 1.606 2009/05/04 11:42:30 danielk1977 Exp $
** $Id: btree.c,v 1.607 2009/05/04 19:01:26 danielk1977 Exp $
**
** This file implements a external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
@@ -4036,14 +4036,13 @@ int sqlite3BtreeMovetoUnpacked(
pCur->aiIdx[pCur->iPage] = (u16)((upr+lwr)/2);
}
for(;;){
void *pCellKey;
i64 nCellKey;
int idx = pCur->aiIdx[pCur->iPage];
int idx = pCur->aiIdx[pCur->iPage]; /* Index of current cell in pPage */
u8 *pCell; /* Pointer to current cell in pPage */
pCur->info.nSize = 0;
pCur->validNKey = 1;
pCell = findCell(pPage, idx) + pPage->childPtrSize;
if( pPage->intKey ){
u8 *pCell;
pCell = findCell(pPage, idx) + pPage->childPtrSize;
i64 nCellKey;
if( pPage->hasData ){
u32 dummy;
pCell += getVarint32(pCell, dummy);
@@ -4057,26 +4056,50 @@ int sqlite3BtreeMovetoUnpacked(
assert( nCellKey>intKey );
c = +1;
}
pCur->validNKey = 1;
pCur->info.nKey = nCellKey;
}else{
int available;
pCellKey = (void *)fetchPayload(pCur, &available, 0);
nCellKey = pCur->info.nKey;
if( available>=nCellKey ){
c = sqlite3VdbeRecordCompare((int)nCellKey, pCellKey, pIdxKey);
/* The maximum supported page-size is 32768 bytes. This means that
** the maximum number of record bytes stored on an index B-Tree
** page is at most 8198 bytes, which may be stored as a 2-byte
** varint. This information is used to attempt to avoid parsing
** the entire cell by checking for the cases where the record is
** stored entirely within the b-tree page by inspecting the first
** 2 bytes of the cell.
*/
int nCell = pCell[0];
if( !(nCell & 0x80) && nCell<=pPage->maxLocal ){
/* This branch runs if the record-size field of the cell is a
** single byte varint and the record fits entirely on the main
** b-tree page. */
c = sqlite3VdbeRecordCompare(nCell, (void*)&pCell[1], pIdxKey);
}else if( !(pCell[1] & 0x80)
&& (nCell = ((nCell&0x7f)<<7) + pCell[1])<=pPage->maxLocal
){
/* The record-size field is a 2 byte varint and the record
** fits entirely on the main b-tree page. */
c = sqlite3VdbeRecordCompare(nCell, (void*)&pCell[2], pIdxKey);
}else{
pCellKey = sqlite3Malloc( (int)nCellKey );
/* The record flows over onto one or more overflow pages. In
** this case the whole cell needs to be parsed, a buffer allocated
** and accessPayload() used to retrieve the record into the
** buffer before VdbeRecordCompare() can be called. */
void *pCellKey;
u8 * const pCellBody = pCell - pPage->childPtrSize;
sqlite3BtreeParseCellPtr(pPage, pCellBody, &pCur->info);
nCell = pCur->info.nKey;
pCellKey = sqlite3Malloc( nCell );
if( pCellKey==0 ){
rc = SQLITE_NOMEM;
goto moveto_finish;
}
rc = sqlite3BtreeKey(pCur, 0, (int)nCellKey, (void*)pCellKey);
c = sqlite3VdbeRecordCompare((int)nCellKey, pCellKey, pIdxKey);
rc = accessPayload(pCur, 0, nCell, (unsigned char*)pCellKey, 0, 0);
c = sqlite3VdbeRecordCompare(nCell, pCellKey, pIdxKey);
sqlite3_free(pCellKey);
if( rc ) goto moveto_finish;
}
}
if( c==0 ){
pCur->info.nKey = nCellKey;
if( pPage->intKey && !pPage->leaf ){
lwr = idx;
upr = lwr - 1;
@@ -4093,7 +4116,6 @@ int sqlite3BtreeMovetoUnpacked(
upr = idx-1;
}
if( lwr>upr ){
pCur->info.nKey = nCellKey;
break;
}
pCur->aiIdx[pCur->iPage] = (u16)((lwr+upr)/2);