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From "Sylvain Lebresne (Commented) (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-2474) CQL support for compound columns
Date Wed, 21 Dec 2011 08:27:32 GMT


Sylvain Lebresne commented on CASSANDRA-2474:

Aright, sorry if it is just me being stupid, but would you mind defining precisely what "dense"
and "sparse" means. I think I know something about CompositeType but somehow those words make
no sense to me. I had more or less gathered that "sparse" was related to the use case where
you have a kwown/finite set of values for the last component, but I have doubts now as 'the
"dense" CompositeType implementation' doesn't mean anything in that context.

I'm also not sure what 'treat missing components as null, allowing adding new columnss in
a straightforward "extension" of the existing CT tuples' exactly refers too. What I can tell
is that if you declare a comparator like CompositeType(IntType, UUIDType, UTF8Type), you can
have columns that have only some prefix of the component (typically '42:92d21d0a-d6cb-437c-9d3f-b67aa733a19f'
is a valid column name for that comparator), and as a consequence it would be possible to
allow 'extend' the preceding comparator to say CompositeType(IntType, UUIDType, UTF8Type,
IntType) (but we cannot right now because we 'cannot change comparator, period').
> CQL support for compound columns
> --------------------------------
>                 Key: CASSANDRA-2474
>                 URL:
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: API, Core
>            Reporter: Eric Evans
>            Assignee: Pavel Yaskevich
>              Labels: cql
>             Fix For: 1.1
>         Attachments: 2474-transposed-1.PNG, 2474-transposed-raw.PNG, 2474-transposed-select-no-sparse.PNG,
2474-transposed-select.PNG, raw_composite.txt, screenshot-1.jpg, screenshot-2.jpg
> For the most part, this boils down to supporting the specification of compound column
names (the CQL syntax is colon-delimted terms), and then teaching the decoders (drivers) to
create structures from the results.

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