Re: [Exist-open] Cursor like functionality

[Hank R. <ha...@cr...>]

Yes, thanks, I considered this, but the potential result set 
is megabytes.  

As it happens, these elements have a child with a unique ID,
so I could cache the "ev-id" element and go back and get the 
whole element one at a time //myNode[ev-id='an-id'] , but 
there is some overhead to this also, even with an index.

So, without yet being familiar with the internals, I wonder 
if the idea of persisting a query result for the life of a
session, so that _start and _howmany work just like a cursor
on subsequent calls -- if the idea has been discussed.

If the url escaped _query matches an existing, and an _start
parameter is present, then, the persisted result set is 
used with no need to re-evaluate the query.

Cheers,
Hank


----- Original Message ----- 
From: "Adam Retter" <ada...@de...>
To: "Hank Ratzesberger" <ha...@cr...>
Cc: <exi...@li...>
Sent: Thursday, November 30, 2006 9:18 AM
Subject: Re: [Exist-open] Cursor like functionality


> If I understand your requirements correctly, This is something that you
> can implement on the application level (we certainly do here). Something
> like this maybe -
> 
> 
> let $resultset := subsequence(session:get-attribute("results"), $start,
> $count) return
> 
> if(empty($resultset))then
> (
> (: perform the query :)
> let $results := //myNode return
> 
> (: cache the results in the http session :)
> session:set-attribute("results", $results)
> )
> else
> (
> (: show the subset of the results :)
> $resultset
> )
> 
> 
> 
> On Thu, 2006-11-30 at 09:01 -0800, Hank Ratzesberger wrote:
>> Hello,
>> 
>> I make some queries that simply cannot be optimized
>> because they compare so many elements.  In a sql 
>> database, I would make the query once and use a cursor
>> to page through the result.
>> 
>> The REST interface conveniently returns the @hits, 
>> @start and @count. Perhaps I am doing something else 
>> wrongly, but calling the same query again, with a 
>> new _start still appears to process the whole long 
>> query again.
>> 
>> Has there been some discussion of a result that 
>> persists for the session, so that the same query with 
>> and new _start works like a cursor?
>> 
>> Thank you,
>> Hank
>> 
>> Hank Ratzesberger
>> NEES Programmer
>> Institute for Crustal Studies
>> University of California, Santa Barbara
>>