[jira] [Updated] (OAK-808) Significant performance issue in TargetImportHandler's prefix mapping handling

["Lukas Eder (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/OAK-808?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Lukas Eder updated OAK-808:
---------------------------

    Attachment: Screen Shot YourKit Profiling Session.png
    
> Significant performance issue in TargetImportHandler's prefix mapping handling
> ------------------------------------------------------------------------------
>
>                 Key: OAK-808
>                 URL: https://issues.apache.org/jira/browse/OAK-808
>             Project: Jackrabbit Oak
>          Issue Type: Bug
>          Components: jcr
>    Affects Versions: 0.7
>            Reporter: Lukas Eder
>         Attachments: Screen Shot YourKit Profiling Session.png
>
>
> While playing around with Oak, I have observed a significant performance bottleneck in 
> {code}
> org.apache.jackrabbit.oak.jcr.xml.TargetImportHandler
> {code}
> The problem can be seen in the attached Screenshot taken from a Yourkit profiling session. The TargetImportHandler contains a reference to a "documentContext" ListMultimap, which acts like a stack of prefix <-> namespace mappings. To the outside, however, it is exposed as "documentPrefixMap", a regular prefix <-> namespace mapping map, which only references the last namespace for a prefix.
> What's problematic here: "documentPrefixMap" is eagerly copied from "documentContext" every time the latter is modified, which may happen a lot in upstream products, such as Adobe CQ5. Instead, "documentPrefixMap" should be a Map view exposing the desired data. An example implementation using Guava:
> {code}
> // Create this view once, in the constructor
> this.documentPrefixMap = Maps.transformValues(documentContext.asMap(),
>     new Function<Collection<String>, String>() {
>         @Override
>         public String apply(Collection<String> input) {
>             return Iterables.getLast(input, null);
>         }
>     });
> {code}
> The above implementation might work, as "documentPrefixMap" is a read-only view of the "documentContext" map. More explicit, verbose implementations may prove to be even faster.
> Before I write a patch, please let me know what you think.

--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira