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https://issues.apache.org/jira/browse/FLINK-12298?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Dawid Wysakowicz updated FLINK-12298:
-------------------------------------
Description:
I would suggest to rework the column functions to a more typesafe approach with
custom {{Range}} class. Right now {{withColumns}} accepts array of Expressions.
We have {{org.apache.flink.table.api.scala.ImplicitExpressionOperations#to}}
method, but also we have implicit conversion from {{scala.Range}} to Expression
range. This already introduces ambiguity, as it is unclear what will be the end
product of expression like {{1 to 9}}. This approach defers the checking of the
types of expressions to expressions resolution phase.
I would suggest to make {{org.apache.flink.table.api.scala.withColumns#apply}}
always accept e.g. {{ColumnRange}} that could always accept only {{Integer}} or
{{String}} instead of Expressions. Such class could look like (this is just a
very rough outline):
{code}
class ColumnRange {
IndexRange idx(Integer idx);
ReferenceRange ref(String reference);
}
class IndexRange {
IndexRange to(Integer idx);
}
class ReferenceRange {
ReferenceRange to(String ref);
}
{code}
> Make column functions accept custom Range class rather than Expression
> ----------------------------------------------------------------------
>
> Key: FLINK-12298
> URL: https://issues.apache.org/jira/browse/FLINK-12298
> Project: Flink
> Issue Type: Improvement
> Components: Table SQL / API
> Reporter: Dawid Wysakowicz
> Priority: Major
>
> I would suggest to rework the column functions to a more typesafe approach
> with custom {{Range}} class. Right now {{withColumns}} accepts array of
> Expressions. We have
> {{org.apache.flink.table.api.scala.ImplicitExpressionOperations#to}} method,
> but also we have implicit conversion from {{scala.Range}} to Expression
> range. This already introduces ambiguity, as it is unclear what will be the
> end product of expression like {{1 to 9}}. This approach defers the checking
> of the types of expressions to expressions resolution phase.
> I would suggest to make
> {{org.apache.flink.table.api.scala.withColumns#apply}} always accept e.g.
> {{ColumnRange}} that could always accept only {{Integer}} or {{String}}
> instead of Expressions. Such class could look like (this is just a very rough
> outline):
> {code}
> class ColumnRange {
> IndexRange idx(Integer idx);
> ReferenceRange ref(String reference);
> }
> class IndexRange {
> IndexRange to(Integer idx);
> }
> class ReferenceRange {
> ReferenceRange to(String ref);
> }
> {code}
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