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https://issues.apache.org/jira/browse/FLINK-3848?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15686458#comment-15686458
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ASF GitHub Bot commented on FLINK-3848:
---------------------------------------
Github user wuchong commented on the issue:
https://github.com/apache/flink/pull/2810
Hi @tonycox , the
[`RowCsvInputFormat`](https://github.com/apache/flink/blob/master/flink-libraries/flink-table/src/main/scala/org/apache/flink/api/table/runtime/io/RowCsvInputFormat.scala#L100)
read columns from left to right and write the value into `holders`. I mean we
should have a `fieldMapping` to determine this value should be put into
`holders` under which index.
I think it will have a better performance than applying a map after that.
> Add ProjectableTableSource interface and translation rule
> ---------------------------------------------------------
>
> Key: FLINK-3848
> URL: https://issues.apache.org/jira/browse/FLINK-3848
> Project: Flink
> Issue Type: New Feature
> Components: Table API & SQL
> Reporter: Fabian Hueske
> Assignee: Anton Solovev
>
> Add a {{ProjectableTableSource}} interface for {{TableSource}} implementation
> that support projection push-down.
> 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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