Re: setFetchSize() [Viruschecked] - Mailing list pgsql-jdbc

Patric Bechtel wrote:

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>On Thu, 17 Jul 2003 13:01:43 -0400, Dmitry Tkach wrote:
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>Hello Dmitry,
>
>that's exactly what the driver is doing if you do a setFetchSize(10).
>Nevertheless, it won't solve the problem of the server eating HUGE amounts of memory if you do a "declare foo cursor
forselect * from myhugetable". It seems  
>like postgresql locks all rows (or even copies them around in memory) until the connection drops again.
>
>
At least one of your two statements above must be wrong :-)
Either it is not the same thing the driver is doing with setFetchSize()
or you are mistaken about the server eating memory and locking rows and
copying them around when you use cursors.

I have never used setFetchSize () (never even seen a driver version
where it was implemented), so, I can't tell you which one is wrong, but
I have been using this cursor approach for almost two years now, in a
huge application, making queries that return tens of millions of rows,
and have never had any locking or memory problems that I could attribute
to a bug in my java code...

Dima

>Patric
>
>
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>>Rich Cullingford wrote:
>>
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>>>All,
>>>Will this function be implemented in Release 7.4? I have several arge
>>>tables that run Java out of memory when I attempt to load them through
>>>JDBC. Any workarounds arppreciated...
>>>
>>>
>
>
>
>>I was using cursors for a while as a workaround...
>>Something like this:
>>
>>
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>>c.setAutocommit (false);
>>Statement s = c.createStatement ();
>>s.execute ("declare foo cursor for select * from bar");
>>
>>
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>>while (true)
>>{
>>   ResultSet rs = s.executeQuery ("fetch 10 from foo");
>>   int count = 0;
>>   while (rs.next ())
>>   {
>>       count++;
>>       doStuffWithThisRow (rs);
>>    }
>>
>>    if (count < 10) //The whole cursor contents has been processed
>>         break;
>>}
>>
>>
>>I hope, it helps...
>>
>>
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>
>>Dima
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