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From Anders Morken <ander...@stud.ntnu.no>
Subject Re: out of memory when writing blobs
Date Wed, 14 Mar 2007 18:14:23 GMT
Mike Matrigali:
> Øystein Grøvlen wrote:
> >For tables with Blob or Clob columns, the default page size for the will 
> >be 32 kB.
> >(Ref. http://db.apache.org/derby/docs/dev/tuning/ctunperf816059.html )
> 
> Currently Derby will never have 2 different page sizes in the same table 
> or index.  As Oystein points out Derby will automatically choose 32k 
> page size if it determines at create table time that is appropriate. 
> Users can override this choice.
> 
> So blobs tend to make page cache bigger because page size is bigger,
> nothing really to do with overflow pages.

Thanks for the correction, both of you. =)

I saw both 4K and 32K pages in the page cache when only one table was
being used, but I guess those 4K pages may have been a primary key index
on the table, or maybe one of the internal tables?

Now that you mention that Derby will never have 2 different page sizes
in the same conglomerate, I realize that I have myself submitted patches
where a page's location is calculated as pageNumber * pageSize. Preceded
a comment by you, Mike, stating that currently there is no mapping from
page number to location other than that simple calculation... So yeah -
I should have known. ;-)

-- 
Anders Morken

My opinions may have changed, but not the fact that I am right!

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