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Overview
| Comment: | Improved comments on the cell-overwrite optimization code. |
|---|---|
| Downloads: | Tarball | ZIP archive |
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA3-256: |
a4fe966da2fc479b18bf521ff5960004 |
| User & Date: | drh 2018-05-07 17:27:04.995 |
Context
|
2018-05-07
| ||
| 18:41 | Activate the cell-overwrite optimization for index b-trees. (check-in: a68697d10e user: drh tags: trunk) | |
| 17:27 | Improved comments on the cell-overwrite optimization code. (check-in: a4fe966da2 user: drh tags: trunk) | |
| 11:48 | On an UPDATE, try to overwrite an existing btree cell with the modified content, if the old and new cell are the same size. Use memcmp() first to avoid dirtying pages that are unchanged. (check-in: 5887d8beb5 user: drh tags: trunk) | |
Changes
Changes to src/btree.c.
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if( pCur->pKeyInfo==0 ){
assert( pX->pKey==0 );
/* If this is an insert into a table b-tree, invalidate any incrblob
** cursors open on the row being replaced */
invalidateIncrblobCursors(p, pCur->pgnoRoot, pX->nKey, 0);
/* If BTREE_SAVEPOSITION is set, the cursor must already be pointing
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if( pCur->pKeyInfo==0 ){
assert( pX->pKey==0 );
/* If this is an insert into a table b-tree, invalidate any incrblob
** cursors open on the row being replaced */
invalidateIncrblobCursors(p, pCur->pgnoRoot, pX->nKey, 0);
/* If BTREE_SAVEPOSITION is set, the cursor must already be pointing
** to a row with the same key as the new entry being inserted.
*/
#ifdef SQLITE_DEBUG
if( flags & BTREE_SAVEPOSITION ){
assert( pCur->curFlags & BTCF_ValidNKey );
assert( pX->nKey==pCur->info.nKey );
assert( pCur->info.nSize!=0 );
assert( loc==0 );
}
#endif
/* On the other hand, BTREE_SAVEPOSITION==0 does not imply
** that the cursor is not pointing to a row to be overwritten.
** So do a complete check.
*/
if( (pCur->curFlags&BTCF_ValidNKey)!=0 && pX->nKey==pCur->info.nKey ){
/* The cursor is pointing to the entry that is to be
** overwritten */
assert( pX->nData>=0 && pX->nZero>=0 );
if( pCur->info.nSize!=0
&& pCur->info.nPayload==(u32)pX->nData+pX->nZero
){
/* New entry is the same size as the old. Do an overwrite */
return btreeOverwriteCell(pCur, pX);
}
assert( loc==0 );
}else if( loc==0 ){
/* The cursor is *not* pointing to the cell to be overwritten, nor
** to an adjacent cell. Move the cursor so that it is pointing either
** to the cell to be overwritten or an adjacent cell.
*/
rc = sqlite3BtreeMovetoUnpacked(pCur, 0, pX->nKey, flags!=0, &loc);
if( rc ) return rc;
}
}else{
/* This is an index or a WITHOUT ROWID table */
/* If BTREE_SAVEPOSITION is set, the cursor must already be pointing
** to a row with the same key as the new entry being inserted.
*/
assert( (flags & BTREE_SAVEPOSITION)==0 || loc==0 );
/* If the cursor is not already pointing either to the cell to be
** overwritten, or if a new cell is being inserted, if the cursor is
** not pointing to an immediately adjacent cell, then move the cursor
** so that it does.
*/
if( loc==0 && (flags & BTREE_SAVEPOSITION)==0 ){
if( pX->nMem ){
UnpackedRecord r;
r.pKeyInfo = pCur->pKeyInfo;
r.aMem = pX->aMem;
r.nField = pX->nMem;
r.default_rc = 0;
r.errCode = 0;
r.r1 = 0;
r.r2 = 0;
r.eqSeen = 0;
rc = sqlite3BtreeMovetoUnpacked(pCur, &r, 0, flags!=0, &loc);
}else{
rc = btreeMoveto(pCur, pX->pKey, pX->nKey, flags!=0, &loc);
}
if( rc ) return rc;
}
}
assert( pCur->eState==CURSOR_VALID || (pCur->eState==CURSOR_INVALID && loc) );
pPage = pCur->pPage;
assert( pPage->intKey || pX->nKey>=0 );
assert( pPage->leaf || !pPage->intKey );
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