[MarkLogic Dev General] Performance of fn:exists(fn:doc($uri))

Danny Sinang d.sinang at gmail.com
Thu Aug 30 12:00:06 PDT 2012


Can anyone recommend a fast way to check for duplicate id's ?

On Thu, Aug 30, 2012 at 2:06 PM, Geert Josten <geert.josten at dayon.nl> wrote:

> That read-locks are URI locks, not fragment locks is something I didn't
> know. Sounds excellent, should have known earlier..
>
> And now the internal code MarkLogic uses to generate id's for all its
> internal objects makes much more sense too..
>
> Mike wrote:
> > To put it more simply: how are you going to guarantee the uniqueness of
> the URI, if not by checking to see if it exists?
>
> I can only think of one other way, by using a write lock on a fixed uri
> (or several fixed uri's), like always doing a
> xdmp:document-insert('/assets/lock', <x/>) before deriving a new uri. But
> that slows down creation processes, likely more than using the read-lock
> approach. :-/
>
> That leaves perhaps only one thing that need attention. If you already
> have many documents, then the likeliness random comes up with an id that
> already exists increases. The average number of attempts it needs to take
> to find an unused number increases over time too. Luckely the range of
> random is very large (20 digits), so you really need quite a very lot of
> documents to even get close to 1/100000 of the space..
>
> :)
>
> Grtz,
> Geert
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