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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-3849) Add FilterableTableSource interface and translation rule
Date Thu, 16 Mar 2017 01:27:42 GMT

    [ https://issues.apache.org/jira/browse/FLINK-3849?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15927277#comment-15927277
] 

ASF GitHub Bot commented on FLINK-3849:
---------------------------------------

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.


> Add FilterableTableSource interface and translation rule
> --------------------------------------------------------
>
>                 Key: FLINK-3849
>                 URL: https://issues.apache.org/jira/browse/FLINK-3849
>             Project: Flink
>          Issue Type: New Feature
>          Components: Table API & SQL
>            Reporter: Fabian Hueske
>            Assignee: Kurt Young
>
> Add a {{FilterableTableSource}} interface for {{TableSource}} implementations which support
filter push-down.
> The interface could look as follows
> {code}
> def trait FilterableTableSource {
>   // returns unsupported predicate expression
>   def setPredicate(predicate: Expression): Expression
> }
> {code}
> In addition we need Calcite rules to push a predicate (or parts of it) into a TableScan
that refers to a {{FilterableTableSource}}. We might need to tweak the cost model as well
to push the optimizer in the right direction.



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