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https://issues.apache.org/jira/browse/PDFBOX-5286?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17424008#comment-17424008
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Andreas Lehmkühler commented on PDFBOX-5286:
--------------------------------------------

The creation of compressed object streams seems to be one of the reasons for 
the degradation. On my system the numbers are 252.324ms vs. 47.233ms for the 
current trunk. AFAIK the current code simply creates new compressed object 
streams instead of reusing the existing one because PDFBox doesn't know if an 
object is new or has been changed.

> Runtime degredation in RC1 and alpha2
> -------------------------------------
>
>                 Key: PDFBOX-5286
>                 URL: https://issues.apache.org/jira/browse/PDFBOX-5286
>             Project: PDFBox
>          Issue Type: Bug
>          Components: Parsing
>    Affects Versions: 3.0.0 PDFBox
>            Reporter: Maruan Sahyoun
>            Priority: Critical
>
> working/reviewing PDFBOX-5068 and PDFBOX-5263 I've experiencing runtime 
> issues for both 3.0.0-RC1 and 3.0.0-alpha2 when loading and saving a large PDF
> https://crossasia-books.ub.uni-heidelberg.de/xasia/reader/download/506/506-42-86246-2-10-20190822.pdf
>  
> ||version||runtime in millis||
> |2.0.24 |2076|
> |3.0.0-RC1 |219472|
> |3.0.0-alpha2 |282284|
> Basic test:
> {code:java}
> long start = System.currentTimeMillis();
> PDDocument pdf = Loader.loadPDF(new File("506-42-86246-2-10-20190822.pdf"));
> pdf.save(new NullOutputStream());
> pdf.close();        
> long end = System.currentTimeMillis();      
> System.out.println("Elapsed Time in milliseconds: "+ (end-start));     
> {code}
> with NullOuputStream
> {code:java}
> package org.apache.pdfbox;
> import java.io.IOException;
> import java.io.OutputStream;
> public class NullOutputStream extends OutputStream {
>     @Override
>     public void write(byte[] b) throws IOException {
>         // don't write anything
>     }
>     @Override
>     public void write(byte[] b, int off, int len) throws IOException {
>         // don't write anything
>     }
>     @Override
>     public void write(int b) throws IOException {
>         // don't write anything
>     }
> }
> {code}
> I've also running tests using JMH - they support these numbers. The 
> difference in numbers for RC1/alpha2 are within a regular variation. 



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