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https://issues.apache.org/jira/browse/ARROW-13167?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17368979#comment-17368979
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Antoine Pitrou commented on ARROW-13167:
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An SQL frontend for Arrow could support that. But compute functions are for
things that *compute*. Not for arbitrary inquiry.
> [C++] Type determination kernels ("type", "type_id")
> ----------------------------------------------------
>
> Key: ARROW-13167
> URL: https://issues.apache.org/jira/browse/ARROW-13167
> Project: Apache Arrow
> Issue Type: Improvement
> Components: C++
> Reporter: Ian Cook
> Priority: Major
>
> The Arrow C++ library exposes an API for determining the data type of an
> expression, but it is exposed as a method of the expression class and it
> requires that the user pass a schema as an argument to the method. This is
> inconvenient; for example, we have had to write some inconsistent code in the
> R bindings to make expression objects carry schemas along with them and then
> pass the schemas to derivative expressions, unifying schemas as needed for
> derivative expressions that take 2+ expressions as arguments.
> This would be much cleaner if we could use the kernel function calling
> interface to call a unary {{type_id}} function that would simply determine
> the type of its input datum and return a scalar integer value from the data
> type enum indicating the its data type. It would be convenient to also have a
> version of this that returned the string description of the data type; I
> think this could be named {{type}}.
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