[jira] [Created] (FLINK-3848) Add ProjectableTableSource interface and translation rule

[Shang Yuanchun (Jira)]

Fabian Hueske created FLINK-3848:
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             Summary: Add ProjectableTableSource interface and translation rule
                 Key: FLINK-3848
                 URL: https://issues.apache.org/jira/browse/FLINK-3848
             Project: Flink
          Issue Type: Task
          Components: Table API
            Reporter: Fabian Hueske


Add a {{ProjectableTableSource}} interface that {{TableSource}}s can implement which support projection.

The interface could look as follows

{code}
def trait ProjectableTableSource {
  def setProjection(fields: Array[String]): Unit
}
{code}

In addition we need Calcite rules to push a projection into a TableScan that refers to a {{ProjectableTableSource}}. We might need to tweak the cost model as well to push the optimizer in the right direction.

Moreover, the {{CsvTableSource}} could be extended to implement {{ProjectableTableSource}}.



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