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https://issues.apache.org/jira/browse/CASSANDRA-196?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12712160#action_12712160
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Jonathan Ellis commented on CASSANDRA-196:
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Yes, we can add a bandaid there, but "iterate in descending order, to add to a
sortedset in ascending order, to reverse before sending back to the client"
isn't exactly awesome. In general exposing an API that looks to the public
like it is low-cost but is really relatively high-cost is a bad idea.
(Yes, we should always do buffered reads, which is why I specifically said we
want to _deserialize_ one at a time" :)
> Doing a descending range still returns columns in ascending order
> -----------------------------------------------------------------
>
> Key: CASSANDRA-196
> URL: https://issues.apache.org/jira/browse/CASSANDRA-196
> Project: Cassandra
> Issue Type: Bug
> Reporter: Jonathan Ellis
>
> 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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