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Overview
| Comment: | Small performance optimization in sqlite3WhereBegin(). |
|---|---|
| Downloads: | Tarball | ZIP archive |
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA3-256: |
39f708d1e286931365a8992dbe7f9001 |
| User & Date: | drh 2017-08-25 13:34:18.937 |
Context
|
2017-08-25
| ||
| 15:43 | Size and performance optimization for sqlite3Init(). (check-in: 776d91284a user: drh tags: trunk) | |
| 13:34 | Small performance optimization in sqlite3WhereBegin(). (check-in: 39f708d1e2 user: drh tags: trunk) | |
| 13:02 | Convert a branch made unreachable by [59560d07] into an assert(). (check-in: 2738b8db3c user: drh tags: trunk) | |
Changes
Changes to src/where.c.
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/* Special case: No FROM clause
*/
if( nTabList==0 ){
if( pOrderBy ) pWInfo->nOBSat = pOrderBy->nExpr;
if( wctrlFlags & WHERE_WANT_DISTINCT ){
pWInfo->eDistinct = WHERE_DISTINCT_UNIQUE;
}
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/* Special case: No FROM clause
*/
if( nTabList==0 ){
if( pOrderBy ) pWInfo->nOBSat = pOrderBy->nExpr;
if( wctrlFlags & WHERE_WANT_DISTINCT ){
pWInfo->eDistinct = WHERE_DISTINCT_UNIQUE;
}
}else{
/* Assign a bit from the bitmask to every term in the FROM clause.
**
** The N-th term of the FROM clause is assigned a bitmask of 1<<N.
**
** The rule of the previous sentence ensures thta if X is the bitmask for
** a table T, then X-1 is the bitmask for all other tables to the left of T.
** Knowing the bitmask for all tables to the left of a left join is
** important. Ticket #3015.
**
** Note that bitmasks are created for all pTabList->nSrc tables in
** pTabList, not just the first nTabList tables. nTabList is normally
** equal to pTabList->nSrc but might be shortened to 1 if the
** WHERE_OR_SUBCLAUSE flag is set.
*/
ii = 0;
do{
createMask(pMaskSet, pTabList->a[ii].iCursor);
sqlite3WhereTabFuncArgs(pParse, &pTabList->a[ii], &pWInfo->sWC);
}while( (++ii)<pTabList->nSrc );
#ifdef SQLITE_DEBUG
{
Bitmask mx = 0;
for(ii=0; ii<pTabList->nSrc; ii++){
Bitmask m = sqlite3WhereGetMask(pMaskSet, pTabList->a[ii].iCursor);
assert( m>=mx );
mx = m;
}
}
#endif
}
/* Analyze all of the subexpressions. */
sqlite3WhereExprAnalyze(pTabList, &pWInfo->sWC);
if( db->mallocFailed ) goto whereBeginError;
/* Special case: WHERE terms that do not refer to any tables in the join
** (constant expressions). Evaluate each such term, and jump over all the
|
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