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https://issues.apache.org/jira/browse/FLINK-3702?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15432945#comment-15432945
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ASF GitHub Bot commented on FLINK-3702:
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Github user ggevay commented on the issue:
https://github.com/apache/flink/pull/2094
> I am a bit out of the loop here. Why do we need a field accessor in the
TypeInformation?
We need this for situations when the user specifies a nested field
expression, which goes through different types. (E.g. `.sum("foo.f1.bar")` on a
POJO, where the field `foo` is a Tuple, and `f1` is a POJO again.) In this
case, getFieldAccessor can recursively call itself on the TypeInformation of
the field, which will be a virtual call that goes to the override for the
field's type.
> DataStream API PojoFieldAccessor doesn't support nested POJOs
> -------------------------------------------------------------
>
> Key: FLINK-3702
> URL: https://issues.apache.org/jira/browse/FLINK-3702
> Project: Flink
> Issue Type: Improvement
> Components: DataStream API
> Affects Versions: 1.0.0
> Reporter: Robert Metzger
> Assignee: Gabor Gevay
>
> The {{PojoFieldAccessor}} (which is used by {{.sum(String)}} and similar
> methods) doesn't support nested POJOs right now.
> As part of FLINK-3697 I'll add a check for a nested POJO and fail with an
> exception.
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