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Pavel Yaskevich edited comment on CASSANDRA-3647 at 7/4/12 10:35 AM:
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bq. We test 6 times for "instanceof CollectionType": one time is to call
serializeForThrift() and 2 other times are to call the execute() methods...
I wouldn't actually judge this by *current* usages of instanceof/casts because
what they show bad tendency where users are forced to use downcasts to get
things which are natural to the complex types but not reflected in the common
AbstractType interface. Every time instanceof is used it indicates that
components' OO design is broken.
If the most common thing we do after cast with CompositeType is get "types"
field then we could add Collection<AbstractType<?>> getComponentTypes() method.
Simple types would return just one component - themselves (or throw an
exception saying that type is not complex to be sure that method is not
misused) and complex ones would be able to return immutable list of their
component types, in combination with isComposite() method that would eliminate
instanceof/downcasts completely.
I don't currently clearly see how to be with CollectionType.execute{Function}
methods but I will think about it.
bq. We cannot do that because Term implements Value. The point of Value is to
be a Term or a Literal.
That means that you are confusing semantics of the "literal" e.g.
https://en.wikipedia.org/wiki/Literal_(computer_programming) , so Term actually
should become {Unary | Single}Literal and implement Literal where {List, Set,
Map} classes would have UnaryLiteral as base element, there is no need to
invent hierarchy like Value.Literal just to make it fit with current Term
implementation.
was (Author: xedin):
bq. We test 6 times for "instanceof CollectionType": one time is to call
serializeForThrift() and 2 other times are to call the execute() methods...
I wouldn't actually judge this by *current* usages of instanceof/casts because
what they show bad tendency where users are forced to use downcasts to get
things which are natural to the complex types but not reflected in the common
AbstractType interface. Every time instanceof is used it indicates that
components' OO design is broken.
If the most common thing we do after cast with CompositeType is get "types"
field then we could add Collection<AbstractType<?>> getComponentTypes() method.
Simple types would return just one component - themselves and complex ones
would be able to return immutable list of their component types, in combination
with isComposite() method that would eliminate instanceof/downcasts completely.
I don't currently clearly see how to be with CollectionType.execute{Function}
methods but I will think about it.
bq. We cannot do that because Term implements Value. The point of Value is to
be a Term or a Literal.
That means that you are confusing semantics of the "literal" e.g.
https://en.wikipedia.org/wiki/Literal_(computer_programming) , so Term actually
should become {Unary | Single}Literal and implement Literal where {List, Set,
Map} classes would have UnaryLiteral as base element, there is no need to
invent hierarchy like Value.Literal just to make it fit with current Term
implementation.
> Support set and map value types in CQL
> --------------------------------------
>
> Key: CASSANDRA-3647
> URL: https://issues.apache.org/jira/browse/CASSANDRA-3647
> Project: Cassandra
> Issue Type: New Feature
> Components: API, Core
> Reporter: Jonathan Ellis
> Assignee: Sylvain Lebresne
> Labels: cql
> Fix For: 1.2
>
>
> Composite columns introduce the ability to have arbitrarily nested data in a
> Cassandra row. We should expose this through CQL.
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