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From Christoph Kiehl <christ...@sulu3000.de>
Subject Re: Total size of a query result and setLimit()
Date Sat, 18 Aug 2007 08:01:33 GMT
Jukka Zitting wrote:
> Hi,
> 
> On 8/17/07, Christoph Kiehl <christoph@sulu3000.de> wrote:
>> Thomas Mueller wrote:
>>> That's a good idea! Implementations that can't support it efficiently
>>> could then calculate the size only when required. What about
>>> getTotalSize()?
>> Implementations should maybe even allowed to return -1 (as on
>> RangeIterator.getSize()) if they do not support this method ...
> 
> I don't like the -1 result. As long as it's allowed, an interoperable
> client must always assume that an implementation may return -1 and
> provide a workaround for such cases.

I don't like it either, but I have absolutely no idea what kind of systems there 
are trying to implement the JCR API and if they are capable of providing a total 
result size. Until now, without setLimit(), they weren't forced to return the 
total size in RangeIterator.getSize() so I thought it might be necessary to 
provide that option for other implementors because at least one off them seems 
to need that -1 return value. But if it isn't necessary I would definitely like 
to skip that option.

> How is the total size question typically solved in cases where an
> application pages through a large database result set? I recall
> sometimes using a separate COUNT(*) query for that, but there may be
> more efficient alternatives.

That's what Thomas suggested as well and I know of no other option.

Cheers,
Christoph


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