[PDFBOX-5824] Allow COSDictionary.MAP_THRESHOLD to be defined as System property

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 3.0.3 PDFBox, 4.0.0
• Fix Version/s: 3.0.3 PDFBox, 4.0.0
• Component/s: PDModel
• Flags: Patch

Language

Java

• Assignee: Andreas Lehmkühler
• Reporter: Jonathan Prates
• Created: 21/May/24 10:35
• Updated: 10/Aug/24 07:18
• Resolved: 14/Jun/24 05:54

Description

COSDictionary.MAP_THRESHOLD 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 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. 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.

Issue Links

• links to: GitHub Pull Request #196