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https://issues.apache.org/jira/browse/SPARK-7562?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14558836#comment-14558836
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Wenchen Fan commented on SPARK-7562:
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After thinking about it, I think we can't just use the ExpectsInputTypes
interface. There are some cases that we don't know the accurate required input
types, like Add, we only need the left and right expressions have same data
type which is numeric.
I have sent a PR to add a `TypeConstraint` interface, which defines when an
Expression has correct data types and what error message should be generated if
type mismatch.
> Improve error reporting for expression data type mismatch
> ---------------------------------------------------------
>
> Key: SPARK-7562
> URL: https://issues.apache.org/jira/browse/SPARK-7562
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Reporter: Reynold Xin
>
> There is currently no error reporting for expression data types in analysis
> (we rely on "resolved" for that, which doesn't provide great error messages
> for types). It would be great to have that in checkAnalysis.
> Ideally, it should be the responsibility of each Expression itself to specify
> the types it requires, and report errors that way. We would need to define a
> simple interface for that so each Expression can implement. The default
> implementation can just use the information provided by
> ExpectsInputTypes.expectedChildTypes.
> cc [~marmbrus] what we discussed offline today.
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