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From "Jonathan Ellis (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-1034) Remove assumption that Key to Token is one-to-one
Date Mon, 28 Nov 2011 14:50:40 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-1034?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13158480#comment-13158480
] 

Jonathan Ellis commented on CASSANDRA-1034:
-------------------------------------------

+1 on the KeyBound approach.  This is exactly what I was hoping for.

Returning to a minor point:

bq. bq. I don't see a good reason to not use a "real" hashcode implementation (Objects.hashCode
is useful here)

bq. Not sure I follow but ByteBuffer.hashCode() does hash the content of the buffer if that
was what you meant.

I mean that straight addition is a weak hashcode combination since X + Y is the same as Y
+ X.  "return Objects.hashCode(X, Y)" is an easy way to do it "right" with no more code than
the weak approach.  Doesn't matter much here but it's good practice imo.

Another nit: should we be using a enum for RowPosition.kind?

Meta observation: I'm glad we're not doing this a week before freeze. :)
                
> Remove assumption that Key to Token is one-to-one
> -------------------------------------------------
>
>                 Key: CASSANDRA-1034
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-1034
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Stu Hood
>            Assignee: Sylvain Lebresne
>            Priority: Minor
>             Fix For: 1.1
>
>         Attachments: 0001-Generify-AbstractBounds-v2.patch, 0001-Generify-AbstractBounds.patch,
0002-Remove-assumption-that-token-and-keys-are-one-to-one-v2.patch, 0002-Remove-assumption-that-token-and-keys-are-one-to-one.patch,
0003-unit-test-v2.patch, 0003-unit-test.patch, 1034_v1.txt, CASSANDRA-1034.patch
>
>
> get_range_slices assumes that Tokens do not collide and converts a KeyRange to an AbstractBounds.
For RandomPartitioner, this assumption isn't safe, and would lead to a very weird heisenberg.
> Converting AbstractBounds to use a DecoratedKey would solve this, because the byte[]
key portion of the DecoratedKey can act as a tiebreaker. Alternatively, we could make DecoratedKey
extend Token, and then use DecoratedKeys in places where collisions are unacceptable.

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