Github user KurtYoung commented on a diff in the pull request:
https://github.com/apache/flink/pull/3520#discussion_r106321885
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/sources/ProjectableTableSource.scala
---
@@ -24,7 +24,7 @@ package org.apache.flink.table.sources
*
* @tparam T The return type of the [[ProjectableTableSource]].
*/
-trait ProjectableTableSource[T] {
+trait ProjectableTableSource[T] extends TableSource[T] {
--- End diff --
It's because i want to unify the PushProjectIntoScan rule codes for both
batch and stream mode. And once we push down project into table source, we not
only should create a new TableScan instance, but also a new TableSource
instance. The codes are like:
```
val newTableSource = originTableSource.projectFields(usedFields)
// create a new scan with the new TableSource instance
val newScan = scan.copy(scan.getTraitSet, newTableSource)
```
At first the `projectFields` method returned `ProjectableTableSource` which
is not a `TableSource`, so i let `ProjectableTableSource` inherit from
`TableSource`. But i just noticed we can just let `projectFields` return one
`TableSource`, and problem resolved.
Will change this.
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