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From "Jonathan Ellis (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-6692) AtomicBTreeColumns Improvements
Date Wed, 12 Mar 2014 23:19:43 GMT


Jonathan Ellis commented on CASSANDRA-6692:

Strongly dislike this pattern:

        if (updateF == null)
            updateF = UpdateFunction.NoOp.instance();

Prefer not modifying parameters (making caller pass NoOp) and optionally adding an assert
to make it obvious.  Will commit with that change.

> AtomicBTreeColumns Improvements
> -------------------------------
>                 Key: CASSANDRA-6692
>                 URL:
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Benedict
>            Assignee: Benedict
>            Priority: Minor
>              Labels: easyfix, performance
>             Fix For: 2.1 beta2
>         Attachments: 6692.3.txt, 6692.fix, patch.txt
> There are two improvements to make to the BTree code that should help:
> 1) It turns out Stack Allocation is more rubbish than we had hoped, and so the fast route
actually allocates garbage. It's unlikely this reduces throughput, but the increased young-gen
pressure is probably unwelcome. I propose to remove the fast route for now.
> 2) It is not uncommon to race to perform an update, so that the new values are actually
out-of-date when we come to modify the tree. In this case the update should recognise that
the original (portion of) the tree has not been modified, and simply return it, without allocating
a new one.

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