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https://issues.apache.org/jira/browse/FLINK-3849?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15927520#comment-15927520
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ASF GitHub Bot commented on FLINK-3849:
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Github user KurtYoung commented on the issue:
https://github.com/apache/flink/pull/3520
Hi @fhueske @godfreyhe, thanks for the review, i addressed most all your
comments.
@fhueske Except for letting `TableSourceScan` be aware of whether filter
has been pushed down. I'm not sure to let the `TableSourceScan` has this kind
of information, i'd prefer to let them stay within the all kinds of
`TableSource`. One drawback to let `TableSourceScan` has such kind of
information is when we do the `TableSourceScan` copy, we need to take care all
these information, make sure they also be copied correctly. In the future, if
we add more extension to `TableSource` like we can push part of query down, we
will face this problem.
Regarding to the interface of `FilterableTableSource`, i agree with you
that the trait containing some logic is not friendly with java extensions. So i
removed the default implementation of `isFilterPushedDown`, the inherited class
should take care of this method. And regarding the `Tuple2` thing, how about we
pass in a mutable java list, and let table source to *pick out* expression from
it and return a copy of table source which contains these pushed down
predicates.
> 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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