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Date: Mon, 24 Jan 2011 11:27:11 +0000 (GMT)
From: Nick Burch <nick.burch@alfresco.com>
To: POI Developers List <dev@poi.apache.org>
Subject: Re: I want to help reduce memory footprint
In-Reply-To: <4D3D25EF.1000103@josephdwagner.info>
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On Sun, 23 Jan 2011, Joseph D. Wagner wrote:
> I am particularly interested in reducing the memory footprint around 
> spreadsheets.  Unfortunately, I must confess that I'm having trouble 
> pealing back all the layers and sifting through all the dependencies.

Which kind - HSSF (.xls) or XSSF (.xlsx)?

> Is there a developer who is familiar with POI's memory consumption who could 
> point me in the right direction?

You'll probably need to run a profiler against the code for your type of 
spreadsheet, and see what bubbles up.

If you're using XSSF, then you probably want to use the File constructor 
rather than the InputStream one. For HSSF, since Christmas there's been an 
experimental POIFS replacement which is more memory efficient, and has a 
File constructor too.

> One specific question I have is where CTCell was defined.  Is it in a 
> library that's outside of POI?

It's auto-generated by XMLBeans based on the Microsoft XSDs. If you do a 
svn checkout, then you can use ant to generate the sources for you through 
XMLBeans. Any optimisations there are likely to need to happen in the 
XMLBeans sourcecode though, to get it to generate a more efficient version

> Also, I know POI relies on XmlBeans.  I was wondering if you were 
> familiar with any issues there, such as "if you cut z in xmlbeans, it 
> will save us a lot of memory."

I'm not aware of anything, sorry. XmlBeans is another apache project, so 
you can ask there, but they usually seem to say "It depends on your XML" 
so you'd probably need to do some profiling first...

Nick

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