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https://issues.apache.org/jira/browse/PDFBOX-5824?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17854124#comment-17854124
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Andreas Lehmkühler commented on PDFBOX-5824:
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I ran some more tests and I can't find any substantial differences concerning
memory consumption. I'm going to remove the SmallMap optimisation from the
trunk and the 3.0 branch.
> Allow COSDictionary.MAP_THRESHOLD to be defined as System property
> ------------------------------------------------------------------
>
> Key: PDFBOX-5824
> URL: https://issues.apache.org/jira/browse/PDFBOX-5824
> Project: PDFBox
> Issue Type: Improvement
> Components: PDModel
> Affects Versions: 3.0.3 PDFBox, 4.0.0
> Reporter: Jonathan Prates
> Assignee: Andreas Lehmkühler
> Priority: Minor
> Fix For: 3.0.3 PDFBox, 4.0.0
>
> Attachments: Screenshot 2024-05-21 at 11.00.25.jpg
>
>
> [COSDictionary.MAP_THRESHOLD|https://github.com/apache/pdfbox/blob/trunk/pdfbox/src/main/java/org/apache/pdfbox/cos/COSDictionary.java#L54]
> controls which Map class is used to optimize memory usage. By default, a
> SmallMap is used. However, if the number of items in a COSDictionary reaches
> the MAP_THRESHOLD value (hardcoded to 1,000), the references [are copied
> |https://github.com/apache/pdfbox/blob/trunk/pdfbox/src/main/java/org/apache/pdfbox/cos/COSDictionary.java#L208]to
> a LinkedHashMap.
> For larger documents, where the COSDictionary is expected to be substantial
> bigger than this limit, this copying occurs frequently. Additionally,
> [SmallMap.keySet is not
> efficient|https://github.com/apache/pdfbox/blob/trunk/pdfbox/src/main/java/org/apache/pdfbox/util/SmallMap.java#L281].
> The attached screenshot shows pdfbox performance with SmallMap (in red)
> versus using LinkedHashMap, ignoring the threshold (in green).
> *Would it be beneficial to allow MAP_THRESHOLD to be defined as a System
> property?*
> If set to 0, LinkedHashMap would be used. If not set, it would default to the
> current MAP_THRESHOLD value and SmallMap, not changing the current behaviour.
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