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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (METAMODEL-195) Scalar function to get key from a MAP type field
Date Sat, 21 Nov 2015 06:59:10 GMT

    [ https://issues.apache.org/jira/browse/METAMODEL-195?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15020290#comment-15020290
] 

ASF GitHub Bot commented on METAMODEL-195:
------------------------------------------

Github user kaspersorensen commented on the pull request:

    https://github.com/apache/metamodel/pull/70#issuecomment-158598709
  
    I stopped a bit because it involved an interface change to ScalaFunction which I think
is kind of a pity - we just launched that interface. But otoh it's maybe better to do the
change early before anyone starts relying too much on it.


> Scalar function to get key from a MAP type field
> ------------------------------------------------
>
>                 Key: METAMODEL-195
>                 URL: https://issues.apache.org/jira/browse/METAMODEL-195
>             Project: Apache MetaModel
>          Issue Type: Improvement
>            Reporter: Kasper Sørensen
>
> Now that we have support for scalar functions, and we also support a host of key/value
or document oriented datastores, I think it would be really natural to support a function
for getting a value inside a map.
> Example:
> {code}
> SELECT MAP_VALUE(address, 'street') FROM contacts
> {code}
> Ideally the function would allow for a full "path" of keys so that you could have maps-within-maps
and so on.
> {code}
> SELECT MAP_VALUE(address, 'homeaddress.street') FROM contacts
> {code}
> Even more ideally we would also add a bit of query parser logic to allow expressing the
path as part of the operand itself:
> {code}
> SELECT address.homeaddress.street FROM contacts
> {code}



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