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https://issues.apache.org/jira/browse/WICKET-6774?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17099335#comment-17099335
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Emond Papegaaij commented on WICKET-6774:
-----------------------------------------
The problem with a single flag for all metadata is that it is difficult to
clear the flag. Every call to {{setMetaData}} would have to check the metadata
to see if the flag needs to be cleared. I've opened a new ticket for the
REMOVALS_KEY: WICKET-6778.
Still, even with the flag, I would like to continue with this branch. I've done
some measurements in serialization size, and the results are very promising:
{{code}}
Plain component: 105716 -> 105716
(identical)
Component with model: 131607 -> 131607
(identical)
Component with simple behavior: 158455 -> 158455
(identical)
Component with model and simple behavior: 211802 -> 201920
(-4.7%)
Component with metadata: 163856 -> 163856
(identical)
Component with model and metadata: 217827 -> 207774
(-4.6%)
Component with simple behavior and metadata: 244125 -> 234250
(-4.0%)
Component with model, simple behavior and metadata: 272992 -> 263039
(-3.6%)
Component with ajax behavior: 226053 -> 144329
(-36.2%)
Component with 2 simple behaviors and 2 metadata-entries: 395546 -> 410538
(+3.8%)
{{code}}
Only the cases where multiple behaviors are combined with a model or metadata
are larger. It may be possible to improve on this by adding specialized classes
for 2 and maybe 3 behaviors. But this will come at a computational and code
complexity cost.
> Separate model, behaviors and metadata into separate fields
> -----------------------------------------------------------
>
> Key: WICKET-6774
> URL: https://issues.apache.org/jira/browse/WICKET-6774
> Project: Wicket
> Issue Type: Improvement
> Components: wicket-core
> Affects Versions: 9.0.0-M5
> Reporter: Thomas Heigl
> Priority: Major
> Attachments: benchmarks.png
>
>
> While investigating performance issues with metadata in WICKET-6771, I
> discovered that significant performance gains can be achieved by separating
> models, behaviors, and metadata into separate fields.
> Currently, all three types of data are stored in a single, untyped field
> {{Component.data}}. The idea is to minimize memory overhead by creating as
> few objects as possible.
> If a model or a single behavior or metadata is added, {{data}} stores only a
> reference to the object. When additional data is added, the reference becomes
> an array.
> This is the most memory-efficient way to store these three types of data. But
> it comes with a cost: code to manipulate that data structure is complex and
> not as efficient because it has to take all possible combinations of data
> into account.
> I suggest introducing 3 separate fields for the 3 types of data, trading a
> little bit of memory for reduced complexity and performance gains.
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