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Alex Petrov commented on CASSANDRA-7826:
----------------------------------------
We can reasonably support nesting for {{map}} and {{set}} nested within
{{map}}. Although complex data types ({{set}} and {{map}}) can (or should) be
reasonably supported only as values. This would also mean that nesting {{map}}
inside of {{set}} (since set elements are serialized into the cell path) would
also not be supported. Allowing them as a key would make the writes much more
complicated, as, for example, in order to update map that has a nested map
element as a key:
{code}
{{a: 1} {b: 2 c: 3}}
{code}
Would result into cell paths with serialised map (schematically speaking): {{
{a: 1} b}} and {{ {a: 1} c }}.
Although having nested collections as value makes most of sense, too, since it
was exactly the point of simplifying nested lookups and allowing deep updates
without re-reading a whole structure.
So far, I've made the cell multi-level and adjusted {{MapType}} and {{SetType}}
to support nested traversals, allowed multi-level {{Value}}s for both Map and
Set. I'd need to do some more adjustments to make it more presentable, but
other than that it starts showing first promises.
> support non-frozen, nested collections
> --------------------------------------
>
> Key: CASSANDRA-7826
> URL: https://issues.apache.org/jira/browse/CASSANDRA-7826
> Project: Cassandra
> Issue Type: Improvement
> Components: CQL
> Reporter: Tupshin Harper
> Assignee: Alex Petrov
> Labels: ponies
> Fix For: 3.x
>
>
> The inability to nest collections is one of the bigger data modelling
> limitations we have right now.
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