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https://issues.apache.org/jira/browse/IGNITE-2263?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15075276#comment-15075276
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Andrey Kornev commented on IGNITE-2263:
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Sergi, you claims of efficiency or inefficiency are based on some unstated (or
half-stated) assumptions.
I must've misunderstood the code you had proposed as a replacement for
collection views. For example, it's not clear to me what isAlwaysFalse() method
does. Besides you efficiency claim is based on size of the source collection.
How "huge" is "huge"? Does one always have to check the size before deciding
whether to use a view or create a copy? Also, on the contrary, filtered
iteration over a collection (regardless of its size) is the sweet spot of
collection views, as is on-the-fly collection transformation.
Finally, while talking about an expected performance benefits of a particular
change one has to take into account all consequences, including the potential
impact on GC. Personally, if I had to choose, I'd always go for less GC and the
collection view is definitely a win in this context.
One more point. isEmpty() can usually be short-circuited by returning as soon
as the filter passes. Also, contains() can be made constant time in special
cases, when the source collection implements Set (otherwise, contains() is
always linear time with or without views).
I'd also recommend dropping GridView class altogether and switching to Guava
(in those few cases where the use of the collection views is warranted). Guava
does excellent job by catching all special cases and making the views extremely
performant.
> Get rid of wrapping views where possible.
> -----------------------------------------
>
> Key: IGNITE-2263
> URL: https://issues.apache.org/jira/browse/IGNITE-2263
> Project: Ignite
> Issue Type: Sub-task
> Components: general
> Affects Versions: ignite-1.4
> Reporter: Vladimir Ozerov
> Assignee: Vladimir Ozerov
> Priority: Critical
> Fix For: 1.6
>
>
> We have about ~50-100 usages of things like F.view or F.viewReadOnly. In lots
> cases it is not necessary, adds garbage, but doesn't add any value.
> Need to revisit these places.
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