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https://issues.apache.org/jira/browse/FLINK-3849?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15927841#comment-15927841
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ASF GitHub Bot commented on FLINK-3849:
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Github user fhueske commented on the issue:
https://github.com/apache/flink/pull/3520
Thanks for the update @KurtYoung!
I think you have a good point about not extending `TableSourceScan`. The
filter pushdown flag might not be the only one. Let's keep this information in
`FilterableTableScan`.
I'm not so sure about the interface of `applyPredicate(predicates:
JList[Expression])`. I think we should not ask users to remove the accepted
Expressions from the `predicates` list. How about we add a method
`getPredicates(): JList[Expression]` which returns the accepted expressions.
This method could also replace `isFilterPushedDown` if we expect `null` if
`getPredicates()` was not called and an empty list if it was called but no
predicate was accepted. IMO, `getPredicates()` has also the advantage that we
can check that the `FilterableTableSource` did not modify the accepted
predicates.
What do you think?
> 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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