[Optimize make-index-mapper and get-instances-limit
clinton@unknownlamer.org**20080115221508
 * Now supports skipping natively and does not cons extra cells
 * Takes a result-fn that is passed the result instead of accumulating
   a list if it is provided
 * Use result-fn in get-instances-limit to fetch instances into local
   list and return that rather than collect in map-inverted-index for
   the fewer results than limit case
 * Now only needed conses are allocated
] {
hunk ./src/database.lisp 9
-(defun make-index-mapper (fn limit)
+(defun make-index-mapper (fn limit &optional (skip 0) result-fn)
hunk ./src/database.lisp 11
-	(results '()))
+	(limit (or limit -1)) ; nil -> no limit
+	(results (list))) 
hunk ./src/database.lisp 17
+	    ((< curr skip) (decf skip) nil)
hunk ./src/database.lisp 19
-	       (car (push (apply fn args) results)))))))
+	       (let ((result (apply fn args)))
+		 (car
+		  (if result-fn
+		      (funcall result-fn result)
+		      (push result results)))))))))
hunk ./src/database.lisp 35
-  (let ((mapper (if limit
-		    (make-index-mapper #'elephant::identity2
-				       (+ limit skip))
-		    #'elephant::identity2)))
-    (nthcdr
-     skip
-     (handler-case
-	 (map-inverted-index mapper
-			     class
-			     slot-name
-			     :start start :end end
-			     :collect t :from-end from-end)
-       (results-limit-reached (c) (values (limit-result c) (limit-count c)))))))
+  (let ((results (list)))
+    (labels ((result-pusher (result) (push result results)))
+      (nreverse
+       (handler-case
+	   (progn
+	     (map-inverted-index (make-index-mapper #'elephant::identity2
+						    limit skip #'result-pusher)
+				 class
+				 slot-name
+				 :start start :end end
+				 :collect nil :from-end from-end)
+	     results)
+	 (results-limit-reached () results))))))
}