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https://issues.apache.org/jira/browse/CALCITE-5570?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17701355#comment-17701355
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Julian Hyde commented on CALCITE-5570:
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I think 0 is OK. It just means it's a 'normal' type that doesn't have type
parameters. (In a good algebraic type system like Standard ML, product (record)
types are not considered 'parameterized' by their field types, nor are sum
(union, enum) types considered 'parameterized' by their alternatives.)
No, it should not be unparsed as "INT ARRAY INT ARRAY MAP ARRAY". Because MAP
takes two arguments it is not suitable as a postfix operator. And because it's
not in the SQL standard there's no need for it to be a postfix operator. It
should be "MAP<INT ARRAY, INT ARRAY> ARRAY". Yeah, it's not perfect.
> Support nested map type for SqlDataTypeSpec
> -------------------------------------------
>
> Key: CALCITE-5570
> URL: https://issues.apache.org/jira/browse/CALCITE-5570
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Reporter: Sergey Nuyanzin
> Assignee: Jiajun Xie
> Priority: Major
> Labels: pull-request-available
> Time Spent: 50m
> Remaining Estimate: 0h
>
> There was added a similar support for arrays/multisets at
> https://issues.apache.org/jira/browse/CALCITE-3250
> however there is no support for maps so far.
> The issue is to add such support.
>
> I think I'd like to clarify is syntax for maps since it has 2 internal
> subtypes for keys and values may be something similar to ROW with delimiter
> like
> {code:sql}
> SELECT CAST(NULL AS MAP(INT, INT));
> -- or with square brackets similar to map constructor
> SELECT CAST(NULL AS MAP[INT, INT]);
> -- or with angle (Flink syntax)
> SELECT CAST(NULL AS MAP<INT, INT>);
> {code}
>
>
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