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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: https://issues.apache.org/jira/browse/CASSANDRA-2474
> 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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