________________________________
> From:
> To: [email protected]
> Date: Fri, 19 Mar 2010 16:16:14 -0500
> Subject: [iText-questions] Perfomance Question - ByteArray vs Files
>
>
> I'm creating a PDF in two passes with my goal to
> end up with it as a file on the server. The first pass creates the PDF and
> the second adds things like headers, footers, etc. using PDFStamper. The
> PDF is being generated from a database so there is a possibility that it could
> get to be large (a few hundred pages?).
This really has nothing to do with itext but some people have discussed
performance
issues and indeed the inner itext implementations may want to vary depending
on what the user can say apriori about some sizes etc. ( for large
tasks, spending some time up front picking a strategy or specific implementation
can pay off). And, of course, I'm a perennial complainer about the resources
related to the PDF file versus alternatives.
First, it may really help if you profile whatever you have- if there is
anything slower
than something called PDF, a highly loaded DB could be it. Do you keep
requesting the same (static) data from it? etc etc.
Of course, trying to do everything "in memory" sounds faster until you
find out that your "memory" is virtual and you keep thrashing. If
you want to rely on the OS great but if you think you can do better
you may benefit from reading/writing to disk the stuff you want
instead of making a huge heap and letting the VM system deal with it.
Once you are all in physical memory, then you want to try
to keep locality and stay in a lower level memory cache ( hard with java).
On some large data sets in other settings, I have used a sort ( yes, another
slow thing)
to stop memory thrashing and speed improvement was order of magnitude (from
essentially unusable to quite tolerable).
So, I guess the most authoritative answer is, it depends.
>
>
>
> Right now I have the PDFWriter directing the output
> to a FileOutputStream. Once that is done, the PDFReader picks it up,
> connects to and uses in PDFStamper to process and send the PDF to the server
> using another FileOutputStream.
>
>
>
> It occurred to me that I might be doing this
> wrong. If PDFReader brings the whole PDF into memory, wouldn't it be
> better to have PDFWriter put the PDF out as a ByteArrayOutputStream which (I
> think) PDFReader can pick up? Or does PDFReader only bring it in as it
> needs it? Or is there some other issue I'm missing....
>
>
>
> I'm not real clear on what the tradeoffs are
> between running everything out files and accepting the I/0 or keeping
> everything in memory.
>
>
>
> Can anyone give me some guidance?
>
>
>
> Thanks!
>
>
>
> Warren
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