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From "ASF GitHub Bot (JIRA)" <>
Subject [jira] [Commented] (METAMODEL-195) Scalar function to get key from a MAP type field
Date Fri, 27 Nov 2015 08:09:10 GMT


ASF GitHub Bot commented on METAMODEL-195:

Github user kaspersorensen commented on the pull request:
    OK I'll try and finish this one up then. I have let it linger for too long, but finally
I think actually it's a pretty good change.

> Scalar function to get key from a MAP type field
> ------------------------------------------------
>                 Key: METAMODEL-195
>                 URL:
>             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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