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From "Sylvain Lebresne (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-7396) Allow selecting Map key, List index
Date Mon, 04 Apr 2016 14:32:25 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-7396?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15224236#comment-15224236
] 

Sylvain Lebresne commented on CASSANDRA-7396:
---------------------------------------------

bq. am I correct, that org.apache.cassandra.db.filter.ColumnFilter.Builder#addSubSelection
would be the "key" method to query individual elements / slices from collections (sets + maps)?

You are.

But I'll note that for this ticket my preference would be to stick to basically expose what
{{ColumnFilter.Builder#addSubSelection}} basically provides internally. In particular, I'd
rather not add anything for lists as we can't make dealing with lists efficient. In fact,
I'd rather make it clear that lists are a second class citizen that is rarely useful and only
if you know what you're doing.

I'm also not entirely convinced by the {{?}} syntax suggested above. In particular, having
{{map?\[key\]}} return a boolean but {{map?\[key1...key2\]}} a set of value is a bit inconsistent.
I'm also not sure that syntax is common enough that it's worth adding specific syntax for
it. We could for instance have {{has(set, key1)}} if we just want to test an element existence.
For {{map?\[key1...key2\]}}, an alternative could be to have a {{keys()}} function that applied
to a map returns the set of keys.


> Allow selecting Map key, List index
> -----------------------------------
>
>                 Key: CASSANDRA-7396
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-7396
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: CQL
>            Reporter: Jonathan Ellis
>            Assignee: Robert Stupp
>              Labels: cql
>             Fix For: 3.x
>
>         Attachments: 7396_unit_tests.txt
>
>
> Allow "SELECT map['key]" and "SELECT list[index]."  (Selecting a UDT subfield is already
supported.)



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