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https://issues.apache.org/jira/browse/METAMODEL-195?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15020292#comment-15020292
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ASF GitHub Bot commented on METAMODEL-195:
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Github user kaspersorensen commented on the pull request:
https://github.com/apache/metamodel/pull/70#issuecomment-158598865
To you example JSON: right now it would only return the first. If we wanted
it to be capable of changing the record count of the resulting dataset then I
guess it's another pretty big change.
> 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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