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https://issues.apache.org/jira/browse/CASSANDRA-4004?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13254128#comment-13254128
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Sylvain Lebresne commented on CASSANDRA-4004:
---------------------------------------------
The idea of my patch is that adding DESC to a field in a table declaration
changes the order of records *logically* (it also does it physically, but that
is an implementation detail). The typical example (which I think is very
common) is for time series, where you're often interested by having record "by
default" in reverse time order (from the more recent to the older). In that
case a SELECT without any ORDER BY would return records directly in reverse
time order. So at least given that definition, no, I don't think there is
anything to do for the code of ORDER BY in SELECT.
I reckon there is another way to add ReversedType, which I'm assuming is what
you are referring to, which consists in *not* changing the logical order, but
to change the physical order. In which case, yes, we would have to take that
into account for ORDER BY during SELECT.
I'll admit I'm less of a fan of that second option though. It seems that
changing the logical order is 1) more natural (to me at least obviously) and 2)
avoids having to use ORDER BY DESC in all your query.
bq. I think I'd prefer to move this into our "implementation extensions"
section as WITH CLUSTERING ORDERED BY (time DESC) or something similar
Why not, but I do prefer "my" notation in that it's more concise and, at least
if it changes the logical order, I guess it doesn't feel like being just an
'implementation extension'.
> 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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