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From "Jonathan Ellis (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-4004) Add support for ReversedType
Date Thu, 19 Apr 2012 16:24:41 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-4004?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13257580#comment-13257580
] 

Jonathan Ellis commented on CASSANDRA-4004:
-------------------------------------------

bq. what happened to "Third (and this is the big one) I strongly suspect that we're going
to start supporting at least limited run-time ordering in the near future" from CASSANDRA-3925

Nothing, except that it's a separate ticket's worth of work.

bq. I never suggested that [ORDER BY depends on disk order], not even a little. Not more than
you did.

I really don't see the distinction between saying "disk order" and "clustering order," as
in "the clustered part of th PK induces an ordering of records ... SELECT without ORDER BY
should return records in that clustering order ... SELECT ORDER BY ASC returns 'z' before
'a'." 

But disk order or clustering order, I don't care which you call it; I reject both as modifiers
of the semantics of DESC.

bq. the fact that value X is larger than Y depends on the ordering induces by your custom
types

Agreed.  But that's not the same as reverse-clustering on a type: "y int ... PRIMARY KEY (x,
y DESC)" (to use your syntax) is NOT the same as "y ReversedInt ... PRIMARY KEY (x, y)." 
In the former, ORDER BY Y DESC should give larger Y before smaller; in the latter, the reverse.

                
> Add support for ReversedType
> ----------------------------
>
>                 Key: CASSANDRA-4004
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4004
>             Project: Cassandra
>          Issue Type: Sub-task
>          Components: API
>            Reporter: Sylvain Lebresne
>            Assignee: Sylvain Lebresne
>            Priority: Trivial
>             Fix For: 1.1.1
>
>         Attachments: 4004.txt
>
>
> It would be nice to add a native syntax for the use of ReversedType. I'm sure there is
anything in SQL that we inspired ourselves from, so I would propose something like:
> {noformat}
> CREATE TABLE timeseries (
>   key text,
>   time uuid,
>   value text,
>   PRIMARY KEY (key, time DESC)
> )
> {noformat}
> Alternatively, the DESC could also be put after the column name definition but one argument
for putting it in the PK instead is that this only apply to keys.

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