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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-1034) Remove assumption that Key to Token is one-to-one
Date Fri, 25 Mar 2011 19:40:05 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-1034?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13011386#comment-13011386
] 

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

I understand the Comparable docs, but 
- that's primarily concerned w/ compareTo + equals b/t members of the same class
- it's valid to say "these are tied for sorting purposes, and yet they are not equal"

In other words I'm more worried about subtle bugs if we allow the equals, than if we don't.
:)

The Map example is a good one -- if I set

map[token(1)] = foo
map[dk(1, 1)] = bar

I would expect two map entries, not one.  (If you want one, you explicitly use asToken, then
there is no ambiguity.)

How about if we add an assert to both equals to make sure we don't pass in the other kind
of object?

> 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: 0.8
>
>         Attachments: 0001-Make-range-accept-both-Token-and-DecoratedKey.patch, 0002-LengthPartitioner.patch,
1034_v1.txt
>
>
> 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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