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https://issues.apache.org/jira/browse/CALCITE-1581?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15827455#comment-15827455
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Julian Hyde commented on CALCITE-1581:
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Good idea.
Let's implement this as two orthogonal features:
* Allow user-defined functions to return a record
* Allow record-valued expressions to be used in the SELECT clause with '... AS
(c1, ..., cn)'
Can you give an example of an implementation of such a function? Would it be a
Java method returning a class?
I'd quibble with describing this as a UDTF (user-defined table function), since
each invocation returns just one record, not a set of records. It's just a UDF
(user-defined function) that returns a record.
> UDTF like in hive
> -----------------
>
> Key: CALCITE-1581
> URL: https://issues.apache.org/jira/browse/CALCITE-1581
> Project: Calcite
> Issue Type: New Feature
> Reporter: Xiaoyong Deng
> Assignee: Julian Hyde
> Labels: udtf
>
> Support one row in and multi-column/multi-row out(one-to-many mapping), just
> like udtf in hive.
> The query would like this:
> {code}
> select
> func(c0, c1) as (f0, f1, f2)
> from table_name;
> {code}
> c0 and c1 are 'table_name' columns. f0, f1 and f2 are new generated columns.
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