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https://issues.apache.org/jira/browse/FLINK-5698?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15892479#comment-15892479
]
ASF GitHub Bot commented on FLINK-5698:
---------------------------------------
Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/3269#discussion_r103958345
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/sources/NestedFieldsProjectableTableSource.scala
---
@@ -0,0 +1,55 @@
+/*
+ * 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
+
+/**
+ * Adds support for projection push-down to a [[TableSource]] with nested
fields.
+ * A [[TableSource]] extending this interface is able
+ * to project the nested fields of the return table.
+ *
+ * @tparam T The return type of the
[[NestedFieldsProjectableTableSource]].
+ */
+trait NestedFieldsProjectableTableSource[T] extends
ProjectableTableSource[T] {
+
+ /**
+ * Creates a copy of the [[NestedFieldsProjectableTableSource]]
+ * that projects its output on the specified nested fields.
+ *
+ * @param fields The indexes of the fields to return.
+ * @param nestedFields hold the nested fields and has identical size
with fields array
+ *
+ * e.g.
+ * tableSchema = {
+ * id,
+ * student<\school<\city, tuition>, age, name>,
+ * teacher<\age, name>
+ * }
+ *
+ * select (id, student.school.city, student.age, teacher)
+ *
+ * fields = field = [0, 1, 2]
+ * nestedFields \[\[], ["school.city", "age"], ["*"\]\]
--- End diff --
That would also be OK with me, but the documentation would need to be
adapted.
> Add NestedFieldsProjectableTableSource interface
> ------------------------------------------------
>
> Key: FLINK-5698
> URL: https://issues.apache.org/jira/browse/FLINK-5698
> Project: Flink
> Issue Type: New Feature
> Components: Table API & SQL
> Reporter: Anton Solovev
> Assignee: Anton Solovev
>
> Add a NestedFieldsProjectableTableSource interface for some TableSource
> implementation that support nesting projection push-down.
> The interface could look as follows
> {code}
> def trait NestedFieldsProjectableTableSource {
> def projectNestedFields(fields: Array[String]):
> NestedFieldsProjectableTableSource[T]
> }
> {code}
> This interface works together with ProjectableTableSource
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