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From "Jonathan Ellis (JIRA)" <>
Subject [jira] Commented: (CASSANDRA-196) Doing a descending range still returns columns in ascending order
Date Tue, 21 Jul 2009 22:33:14 GMT


Jonathan Ellis commented on CASSANDRA-196:

add(0) is a bad operation to do on a ArrayList, we should probably either use a deque or just
do Collections.reverse at the end of the adds.

other than that it looks fine to me.

can you add a test slicing super subcolumns too?

> Doing a descending range still returns columns in ascending order
> -----------------------------------------------------------------
>                 Key: CASSANDRA-196
>                 URL:
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>            Reporter: Jonathan Ellis
>            Assignee: Jun Rao
>             Fix For: 0.4
>         Attachments: 196-systest.patch, issue196.patchv3, issue_196.patchv2
> If I do
>         result = table.getSliceFrom(row, "Standard1:col5", false, 2);
>         cf = result.getColumnFamily("Standard1");
> I expect to get back columns in the order 5, 4, 3 (at the thrift level, it's turned into
a list) but instead I get 3, 4, 5 because using a CF as the return vehicle re-sorts them by
the standard comparator.
> The simplest solution is to allow user-defined column ordering as in CASSANDRA-185 and
always return columns in that order (i.e., remove the ascending bool).  This also allows us
to make the columngroup fetching more efficient in the best case (deserializing one column
at a time instead of a group at a time).
> OTOH using one index to allow fetching items relatively efficiently in either directly
is cool.  But my gut says it's relatively uncommon to want to access in both directions at
once, and even more uncommon to not be able to do a reverse() on the client side (because
of data volume, for instance).  Forcing a separate CF for this special case of a special case
might be worth the tradeoff.

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