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From: Andrus Adamchik <andrus@objectstyle.org>
To: user@cayenne.apache.org
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Subject: Re: Big selects on PostGres : Configuring Statement.setFetchSize() of
 a selectquery
Date: Fri, 15 May 2009 22:08:49 +0300
References: <23555842.post@talk.nabble.com>
 <3219fff70905150203m5b64fa23o1000be94502fc881@mail.gmail.com>
 <23560831.post@talk.nabble.com>
 <C370FE67-9C8F-4014-9E42-96C1A8244067@roxanemy.com>
 <23561312.post@talk.nabble.com>

I haven't experimented with that much (so no idea which drivers take  
advantage of that and which would simply ignore it), but that would  
indeed be a useful parameter for ResultIterator scenario. So maybe  
open a feature request in Jira?

Andrus


On May 15, 2009, at 5:45 PM, stefcl wrote:

>
> Thanks,
>
> Since the beginning I am convinced that resultiterators are the  
> right way,
> unfortunately they are useless if the jdbc driver loads everything  
> in memory
> before giving access to the resultset.
>
> I hope there's something to do about it because it's a showstopper  
> for me.
>
>
> Robert Zeigler-6 wrote:
>>
>> Take a look at paginated queries (which isn't /quite/ what you want,
>> but may help you):
>>
>> http://cayenne.apache.org/doc/paginated-queries.html
>>
>> As well as ResultIterator:
>> http://cayenne.apache.org/doc/iterating-through-data-rows.html
>>
>> Robert
>>
>> On May 15, 2009, at 5/159:21 AM , stefcl wrote:
>>
>>>
>>>
>>> Thanks but my problem is not related to paging.
>>>
>>> I would like to be able to execute a select query which returns  
>>> approx
>>> 100000 rows with a single selectQuery and process them one by one,
>>> while
>>> keeping only a few of them in memory (using the resultiterator).
>>>
>>> In jdbc, Statement.setFetchSize(1000) tells the jdbc driver to
>>> retrieve
>>> results from the database 1000 at a time and ask for the next 1000
>>> as you're
>>> iterating the resultset. Otherwise its default behavior is to
>>> retrieve the
>>> 100'000 rows in memory before you can start iterating the resultset.
>>>
>>> It's not the same thing as inserting a TOP or a LIMIT clause in the
>>> query.
>>>
>>> Any help appreciated
>>>
>>>
>>> Andrey Razumovsky wrote:
>>>>
>>>> Hi,
>>>>
>>>> Yes of course. You can use SelectQuery.setFetchLimit(int) and
>>>> setFetchStart(int) methods. They do just that.
>>>>
>>>> Andrey
>>>>
>>>
>>> -- 
>>> View this message in context:
>>> http://www.nabble.com/Big-selects-on-PostGres-%3A-Configuring-Statement.setFetchSize%28%29-of-a-selectquery-tp23555842p23560831.html
>>> Sent from the Cayenne - User mailing list archive at Nabble.com.
>>>
>>
>>
>>
>
> -- 
> View this message in context: http://www.nabble.com/Big-selects-on-PostGres-%3A-Configuring-Statement.setFetchSize%28%29-of-a-selectquery-tp23555842p23561312.html
> Sent from the Cayenne - User mailing list archive at Nabble.com.
>
>