[xquery-talk] search mechanism

Wolfgang Meier wolfgang at exist-db.org
Thu Apr 6 22:31:19 PDT 2006

Hi Peter,

 > for $doc in //text
 > where $doc//abstract &= 'peter' and $doc//date &= 'java'
 > order by $doc//date
 > return xs:string($doc/@id)

Yes, it looks right, though you could also use a predicate instead of
the "where": for $doc in //text[.//abstract &= 'peter' and .//date &=
'java'] ... Some implementations prefer predicates over "where"
expressions ;-)

 > At least it seems to do what I want it to. I would just create this 
 > query string and then pass it to the service.compile() method. Is there
 > something wrong with doing it this way?

No, that's ok. However, I proposed to use the eval function because
you could then do the entire processing in XQuery - no need for Java.
You would then have a main XQuery which constructs the query fragment
above as a string, passes it to eval and post-processes the results.
But I don't know enough about the context of your application. I
prefer to write my entire (web-)applications in XQuery if I can (and
use Java only for extension functions).

 > Thank you for your hint! But couldn't this approach cause problems if 
a user
 > opens up a second window (e.g. in IE) and starts a second search 
within the
 > same session?

You could assign a unique id to every query and store the results into
the session with this id (then you just have to take care to time out
the saved queries after a while). Or you allow the user to explicitely
save the results into the db.

 >> Unless you evaluate XQuery using indexes, in which case the less
 >> explicit paths, and the more "//" operators that you use, the better.
 >> John
 >Am I mistaken if I think that for eXist the latter is true?

Yes, correct. a//d should be faster than a/b/c/d as we can directly
lookup up all "d" elements in the index.


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