Re: [bdbxml] Sort Query Performance

Hello John,
can you please tell me exactly what to do to sove this problem?
thanks

John Snelson wrote:

> There are two issues here. First is that with or without the "order 
> by" clause, your query is returning nodes from every document in the 
> database. This will always take a while, but the response time (time 
> until first answer) can be sped up by using lazy evaluation.
>
> The second is that the "order by" clause effectively detroys lazy 
> evaluation, because it has to gather all the answers before it can 
> sort them all and return them. Presently, DB XML does not use indexes 
> to optimise "order by" clauses - but this work is planned for the 
> future, and high priority.
>
> With the next release of DB XML, the XmlContainer::lookupIndex() 
> methods will return their results in sorted index order. If your 
> "order by" clause directly corresponds to an index, it will be 
> possible to use this method to manufacture fast sorted results.
>
> I hope this helps,
>
> John
>
> M Chaudhary wrote:
>
>> Hello friends ,
>> I am using dbxml 2.1.8 version .
>> I am executing a sort query on a container with more than 10000 
>> documents , but the execution
>> of the query is taking a lot of time(more than 15 mins).
>> The query is as follows --
>> 'for $i in collection("xyz.dbxml")/root/x order by $i/y[@a="abc"]/@b 
>> descending  return $i'
>>
>> I have indexed the container as follows : -
>>
>> Index: node-attribute-equality-string for node {}:id
>> Index: node-attribute-equality-string for node {}:a
>> Index: node-attribute-presence-none to node: {}:b
>>
>> and the Xml Structure is as follows --
>>
>>
>> ------XML structure ------
>>
>> <root id = "pqr" >
>>        <x>
>>            <y a="abc" b="300"> </y>
>>        <y a="def" b="123"> </y>
>>        <y a="pqr" b="432"> </y>
>>        ...
>>        ...
>>    </x>
>>    ...
>>    ...
>>    ...
>>    ...
>> </root>
>>
>>
>> Can you please suggest me what should I do make the query execution 
>> faster ?
>> Thank You !
>> Regards ,
>> Ajinkya N
>>
>>
>> ------------------------------------------
>> To remove yourself from this list, send an
>> email to [email protected]
>>
>
>


------------------------------------------
To remove yourself from this list, send an
email to [email protected]