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https://issues.apache.org/jira/browse/FLINK-3849?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15878669#comment-15878669
]
ASF GitHub Bot commented on FLINK-3849:
---------------------------------------
Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/3166#discussion_r102492031
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/sources/FilterableTableSource.scala
---
@@ -0,0 +1,38 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.table.sources
+
+import org.apache.flink.table.expressions.Expression
+
+/**
+ * Adds support for filtering push-down to a [[TableSource]].
+ * A [[TableSource]] extending this interface is able to filter the
fields of the return table.
+ *
+ */
+trait FilterableTableSource {
+
+ /** return an predicate expression that was set. */
+ def getPredicate: Array[Expression]
+
+ /**
+ * @param predicate a filter expression that will be applied to fields
to return.
--- End diff --
The method docs should be more extensive. We have to explain that the
expressions in the array are conjunctive terms which have to be accepted
completely or not at all. All non-accepted terms have to be returned unmodified.
> 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: Anton Solovev
>
> 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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