Github user fhueske commented on the issue:
https://github.com/apache/flink/pull/2810
This is a good question @tonycox. First of all, we need to agree on the
semantics of the `ProjectableTableSource.setProjection()` method. IMO, the
table source must return a `DataSet` (or `DataStream`) with the fields in the
order requested by `setProjection()`. If the `InputFormat` (or
`SourceFunction`) is not able to control the order of fields, the table source
needs to add a `MapFunction` to fix the order. This would happen in
`BatchTableSource.getDataSet()` (or `StreamTableSource.getDataStream()` and
hence be opaque to Calcite and not involve a `LogicalCalc`.
From a performance point of view I agree with @wuchong that it would be
good to have correct records produced by the `RowCsvInputFormat`. However, I
would see this as a "nice to have" feature. If you do not want to include it,
it would be nice if you could open a JIRA to address this issue at some later
point in time.
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