Scan an index instead of a table for "SELECT count(*) FROM <tbl>" queries. Because an index is usually smaller than a table on disk, this saves some IO. (CVS 6315)

FossilOrigin-Name: 294ba6f743c9132dce0e73da480bd3c2071e7239

src/delete.c

@@ -12,7 +12,7 @@
 ** This file contains C code routines that are called by the parser
 ** in order to generate code for DELETE FROM statements.
 **
-** $Id: delete.c,v 1.193 2009/02/20 10:58:42 danielk1977 Exp $
+** $Id: delete.c,v 1.194 2009/02/23 17:33:50 danielk1977 Exp $
 */
 #include "sqliteInt.h"
 
@@ -395,6 +395,7 @@ void sqlite3DeleteFrom(
     /* Collect rowids of every row to be deleted.
     */
     sqlite3VdbeAddOp2(v, OP_Null, 0, iRowSet);
+    pTabList->a[0].usesRowid = 1;
     pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, 0,
                                WHERE_FILL_ROWSET, iRowSet);
     if( pWInfo==0 ) goto delete_from_cleanup;