[
https://issues.apache.org/jira/browse/PDFBOX-5499?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17600725#comment-17600725
]
Michael Klink commented on PDFBOX-5499:
---------------------------------------
{quote}How about that we replace the SmallMap at runtime with a LinkedHashMap
if the count exceeds some arbitrary number, e.g. 100 ?
{quote}
It would be worth a try.
There is one tiny behavior change associated with that, though: According to
the {{Map}} interface JavaDocs the derived collections of the map,
{{{}entrySet{}}}, {{{}keySet{}}}, and {{{}values{}}}, shall be backed by the
map itself. {{SmallMap}} violates this requirement, {{LinkedHashMap}}
implements it correctly.
Thus, code using the {{COSDictionary}} methods {{{}entrySet{}}},
{{{}keySet{}}}, and {{getValues}} may have to deal with a changing behavior: As
long as the map is a {{SmallMap}} these collections are not backed by the
underlying map, but as soon as it is replaced by a {{{}LinkedHashMap{}}}, they
suddenly are.
(Most usages will ignore the difference as the returned collections usually are
used only once...)
> Performance issue since 2.0.18
> ------------------------------
>
> Key: PDFBOX-5499
> URL: https://issues.apache.org/jira/browse/PDFBOX-5499
> Project: PDFBox
> Issue Type: Bug
> Components: PDModel
> Affects Versions: 2.0.19
> Reporter: Thomas Debray Luyat
> Priority: Major
> Attachments: image-2022-09-05-12-48-04-608.png,
> image-2022-09-05-17-37-55-155.png, image-2022-09-05-17-40-22-416.png,
> image-2022-09-05-19-55-40-753.png
>
>
> Our PDF is parsed in less than 200ms in 2.0.18 and more then 8 seconds in
> 2.0.19. The same issue is still there in 2.0.26.
>
> In version 2.0.19, SmallMap has been introduced. We're facing a performance
> issue since this modification.
> !image-2022-09-05-12-48-04-608.png|width=968,height=377!
> We patch our code to just replace the SmallMap implementation like this:
> {code:java}
> package org.apache.pdfbox.util;
> import java.util.LinkedHashMap;
> public class SmallMap<K, V> extends LinkedHashMap<K, V> {
> // nothing : use the standard LinkedHashMap
> }{code}
> And the performance issue disappear.
> Our test is really simple:
> {code:java}
> long start = System.currentTimeMillis();
> try (PDDocument document = PDDocument.load(new File(inFile))) {
> // nothing : only parsing is evaluated
> }
> long duration = System.currentTimeMillis() -start;
> assertTrue(duration < 500);{code}
>
> I can understand that the SmallMap can solve issues in some cases, but it is
> possible to implement a factory to create this map and then allow to setup
> which Map implementation we want to use?
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
