Andres de la Peña created CASSANDRA-18085:
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Summary: Add support for singletons on CQL collection functions
Key: CASSANDRA-18085
URL: https://issues.apache.org/jira/browse/CASSANDRA-18085
Project: Cassandra
Issue Type: Improvement
Components: CQL/Semantics
Reporter: Andres de la Peña
Assignee: Andres de la Peña
CASSANDRA-18060 has added generic CQL functions to get the min, max, sum, avg
and number of items in a collection. These functions can only be applied to
collection values. The functions throw an {{InvalidRequestEception}} when
applied to not-collection values.
CASSANDRA-18078 has been pointed out that those functions could be applied also
to not-collection values, considering that the not-collection argument can be
considered a collection of a single element. For example:
* collection_min(7) = collection_min([7]) = collection_min(\{7}) = 7
* collection_max(7) = collection_max([7]) = collection_max(\{7}
) = 7
* collection_sum(7) = collection_sum([7]) = collection_sum(\{7}) = 7
* collection_avg(7) = collection_avg([7]) = collection_avg(\{7}
) = 7
* collection_count(7) = collection_count([7]) = collection_count(\{7}
) = 1
This would be particularly useful when used in combination with functions such
as {{writetime}} and {{{}ttl{}}}. Those functions can return either single
values or collections of values depending on whether the column passed as
argument is multicell. Thus, users interested on getting the min/max/sum/avg of
the writetimes/ttls of a column need to consider the type of the column when
choosing what functions they should use. With the proposed change they could
just use, for example, {{collection_max(writetime(column))}} regardless of the
column type.
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