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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 Tue, 09 Nov 2010 04:54:08 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-1034?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12929953#action_12929953
] 

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

bq. it's very convenient to be able to use the "natural" compareTo to compare those two kinds
of DK

In particular, we generate (Token, null) DKs for range scans, at least in part because Hadoop
thinks in terms of TokenRanges instead of DecoratedKeyRanges.  (Presumably it is still ok
to assume that a partitioner generates many more tokens than there are nodes in the cluster;
if not, this would need to change.)

We might be able to still do this, if we just say that DK(T, null) always sorts before DK(T,
non-null-key) for any given Token T.

I still suspect we're using DK in some places where Token is all we really need.

> 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
>            Priority: Minor
>
> 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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