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Date: Fri, 10 Aug 2012 16:36:03 +0400
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 <CAAwi-j_numiezm1TjgXsyJX=RfuChuOfo6DD+42+ULPxyh2Z2w@mail.gmail.com>
Subject: Re: Memory consumption
From: Yegor Kozlov <yegor.kozlov@dinom.ru>
To: POI Users List <user@poi.apache.org>
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You are reading data from a database, can it be the bottleneck?
SXSSF is a low-memory footprint API and I doubt it cause spikes up to 1.3GB.

Can your application cache objects ? Also, check settings of the JDBC
driver and make sure it streams data and does not accumulate it in
memory.

Yegor

On Fri, Aug 10, 2012 at 1:13 PM, Oliver Kohll - Mailing Lists
<oliver.lists@gtwm.co.uk> wrote:
> Hi,
>
> I have a servlet which generates Excel files using POI and serves them as downloads. I've hit a heap space issue generating large(ish) files.
>
> A file that ends up as 20MB, 300,000 rows causes a memory spike of about 1.3GB. A smaller 1MB file with a few thousand rows causes a 30 or 40 MB jump.
>
> I've done everything I can think of so far:
>
> I use the streaming excel generation class SXSSFWorkbook which I understand is low memory, buffering to disk.
>
> There are two methods, one to generate the Excel and one to serve it. I save a temporary file to disk rather than transfer data directly in memory between the methods
>
> The second method to serve the content uses buffered input and output streams.
>
> Anything else you can think of? The code is here:
>
> https://github.com/okohll/agileBase/blob/master/gtpb_server/src/com/gtwm/pb/servlets/ReportDownloader.java
>
> getSessionReportAsExcel generates the spreadsheet and
>
> serveSpreadsheet serves it.
>
>
> Oliver Kohll
> www.agilebase.co.uk
>
>
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