[elephant-devel] map-btree from-end arg not working?

[Ian Eslick]

Let me look at the history for that file.  I can't remember if I  
fixed some of this on the working branch (darcs) or back during the  
0.9.0 release.  There are a bunch of subtle interactions that can  
disturb each other, but that does look like a problem doesn't it?

Ian


On Sep 8, 2007, at 3:28 PM, Chris Laux wrote:

> So I had a look at it myself and it turned out to be much easier  
> than I
> had expected, which is what kept me from trying in the first place.
>
> The following method in src/db-bdb/bdb-collections.lisp is the  
> culprit:
>
> (defmethod cursor-prev ((cursor bdb-cursor))
>   (if (cursor-initialized-p cursor)
>       (let ((sc (get-con (cursor-btree cursor))))
> 	(with-buffer-streams (key-buf value-buf)
> 	  (multiple-value-bind (key val)
> 	      (db-cursor-move-buffered (cursor-handle cursor)
> 				       key-buf value-buf :prev t)
> 	    (if (and key (= (buffer-read-oid key) (cursor-oid cursor)))
> 		(values t (deserialize key sc)
> 			(deserialize val sc))
> 		(setf (cursor-initialized-p cursor) nil))))
> 	(cursor-last cursor))))
>
> That "cursor-last" call at the end looks very suspicious, and indeed
> removing it solves the problem. But I don't know where it belongs  
> or if
> it can be safely removed. Any ideas?
>
> Cheers,
>
> Chris Laux
>
>
> Chris Laux wrote:
>> Hi again,
>>
>> I seem to have stumbled across another bug: the from-end argument
>> doesn't seem to be working, map-btree always calls with the same
>> (presumably last) entry when it is set.
>>
>> (defun test-btree-from-end (btree from-end)
>>   (let (acc
>> 	(n 0))
>>     (map-btree #'(lambda (k v)
>> 		   (push (list k v) acc)
>> 		   (when (= (incf n) 4)
>> 		     (return-from test-btree-from-end acc)))
>> 	       btree :from-end from-end)))
>>
>>> (test-btree-from-end ** nil)
>> ((3398012969 #<MESSAGE oid:227324>) (3398012898 #<MESSAGE oid: 
>> 226751>)
>>  (3398012815 #<MESSAGE oid:226044>) (3398012772 #<MESSAGE oid: 
>> 225621>))
>>
>>> (test-btree-from-end *** t)
>> ((3398231130 #<MESSAGE oid:552110>) (3398231130 #<MESSAGE oid: 
>> 552110>)
>>  (3398231130 #<MESSAGE oid:552110>) (3398231130 #<MESSAGE oid: 
>> 552110>))
>>
>> My setup is BerkeleyDB 4.5.20 with Elephant 0.9.0 with SBCL 1.0.4 on
>> Linux/x86-64.
>>
>> Thanks,
>>
>> Chris Laux
>>
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