[xquery-talk] paging mechanism

[Peter Mueller]

Hi Philippe,

> Your first problem:
> 
>   for $x at $pos in 
>     for $y in $doc/body/idno
>     order by xs:decimal($x) ascending 
>     return $y
>   where ($pos mod 50) < 2
>   return $x

I tried your query, but it didn't work for me.

It seems that you didn't replace the $doc by $x (?) and didn't put in a
place to to bind to in the first line (?).

[ I am quite new to XQuery - so please excuse that I might not understand
your query and am not very familiar with the general syntax! ]

I tried this query:

for $x at $pos in //text/body/idno
for $y in $x/body/idno
order by xs:decimal($x) ascending 
return $y
where ($pos mod 50) < 2
return $x

but still I got an error message telling me that (on line 5) there was an
'unexpected token "null" beyond end of query'

Do you have any ideas what I did wrong?

Thanks in advance,
Peter

P.S. I attached the test file so that you know the structure of the
collection.


 
> The casting is kind of important, otherwise you may risk getting
> lexicographic 
> ordering, when the numbers don't have leading zeros. Also, you must use
> the 
> for-loop position binding.
> 
> The second problem should then solve itself, but don't for get to use the 
> ordered version of the input there. It may be a good idea to sort the
> input 
> first and put it in a variable.
> 
> Does that make sense?
> -Ph
> 
> On Friday 03 February 2006 11:09, Peter Mueller wrote:
> > Hi everybody,
> >
> > here is what I am trying to achieve ...
> >
> > I would like to implement a paging mechanism that offers access to
> several
> > collections with between 500 and 3000 documents.
> >
> > When the web user selects one collection he should be presented with
> some
> > kind of sub folder hierarchy where each "sub folder" contains "chunks"
> of -
> > lets say 50 - documents. These "sub folders" should be labeled with the
> > time period they belong to (to allow the user more specific access),
> e.g.:
> > 1980-1983
> > 1983-1986
> > 1986-1987
> > and so on...
> > (PROBLEM 1!)
> >
> > If a user then chooses one time interval (lets say "1980-1983") he
> should
> > be given a navigating structure (like [1-10] [11-20] ... [41-50])
> (trivial
> > if PROBLEM 2 is solved --> see below) along with some metadata of the
> first
> > 10 "hits" (PROBLEM 2!).
> >
> >
> > PROBLEM 1:
> > For solving the first problem I need to first sort the documents (by
> date)
> > and then extract the years from which the 1st, the 50th, the 51st and so
> on
> > documents originate.
> >
> > For this tried a couple of queries (see below) which unfortunatelly
> didn't
> > yield the expected results (using SAXON).
> >
> > I tested my query on just one xml file which contains 147
> test-documents.
> >
> > [I used <idno> instead of <date> for sorting and as result because it's
> > easier for testing.]
> >
> > for $doc in //text
> > order by $doc/body/idno
> > ascending return
> > if($doc[(position() mod 50) < 2])then
> > (
> > $doc/body/idno
> > )
> > else()
> >
> > Instead of the expected:
> > <idno>001</idno>
> > <idno>050</idno>
> > <idno>051</idno>
> > <idno>100</idno>
> > <idno>101</idno>
> >
> > ... I got the idno of all the docs:
> > <idno>001</idno>
> > <idno>002</idno>
> > <idno>003</idno>
> > ...
> > <idno>147</idno>
> >
> >
> > The same happended when I replaced the line
> > if($doc[(position() mod 50) < 2])then
> > with
> > if((position() mod 50) < 2)then
> >
> > Finally, I tried:
> >
> > for $id at $pos in //text/body/idno
> > order by xs:integer($id) ascending
> > return
> > if ($id[$pos mod 50 < 2]) then $id
> > else ()
> >
> > leaving me with:
> >
> > <idno>012</idno>
> > <idno>047</idno>
> > <idno>059</idno>
> > <idno>117</idno>
> > <idno>123</idno>
> >
> > Do you have any suggestions as to how this could work correctly?
> >
> >
> >
> > PROBLEM 2:
> > For solving the second problem I would need the same sorting as above
> and
> > then extract some metadata from the documents at position number 1 to 10
> > (11-20, etc...) in the resulting sequence.
> >
> > To solve this I tried:
> >
> > declare variable $startIndex as xs:integer := 1;
> > declare variable $pageSize as xs:integer := 10;
> > for $idno in
> > fn:subsequence( //text/body/idno, $startIndex, $pageSize)
> > order by $idno
> > return $idno
> >
> > instead of the expected:
> > <idno>001</idno>
> > <idno>002</idno>
> > <idno>003</idno>
> > ...
> > <idno>010</idno>
> >
> > I got:
> > <idno>001</idno>
> > <idno>004</idno>
> > <idno>005</idno>
> > <idno>007</idno>
> > <idno>009</idno>
> > <idno>010</idno>
> > <idno>011</idno>
> > <idno>012</idno>
> > <idno>020</idno>
> > <idno>024</idno>
> >
> > Again, do you have any idea what went wrong?
> >
> > Thank you very much for your help!
> >
> > Best wishes,
> > Peter
> _______________________________________________
> talk at xquery.com
> http://xquery.com/mailman/listinfo/talk
> 

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