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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-1005) Add different mutable-object modes to runtime
Date Wed, 01 Oct 2014 10:03:33 GMT

    [ https://issues.apache.org/jira/browse/FLINK-1005?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14154622#comment-14154622

ASF GitHub Bot commented on FLINK-1005:

Github user StephanEwen closed the pull request at:


> Add different mutable-object modes to runtime
> ---------------------------------------------
>                 Key: FLINK-1005
>                 URL: https://issues.apache.org/jira/browse/FLINK-1005
>             Project: Flink
>          Issue Type: Improvement
>          Components: Local Runtime
>    Affects Versions: 0.6-incubating
>            Reporter: Stephan Ewen
>            Assignee: Stephan Ewen
>             Fix For: 0.7-incubating
> Currently, the runtime works strictly with mutable objects. That means that as few objects
as possible (typically one or two) are reused for the data records all the time. Objects are
cloned/restored, though, at various places to ensure that the contents is fresh at every call.
> The rational behind this was to reduce pressure on the garbage collector. In fact, you
can run programs where no garbage collection happens (if the UDFs are written to reuse objects
as well).
> It can, however, lead to bugs in not-carefully written user code.
> I propose to add two modes to the runtime:
>   - No-object-reuse (default) mode. New objects for every record. Safe but potentially
>   - Object-reusing mode - All objects are reused, without backup copies.. The UDFs must
be careful to not keep any objects as state or not to modify the objects,

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