org.apache.flink.table.sources.NestedFieldsProjectableTableSource.scala Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one
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* distributed with this work for additional information
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* 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,
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*/
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 returned table.
*/
trait NestedFieldsProjectableTableSource {
/**
* Creates a copy of the [[TableSource]] that projects its output on the specified nested fields.
*
* @param fields The indexes of the fields to return.
* @param nestedFields The accessed nested fields of the fields to return.
*
* 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 \[\["*"], ["school.city", "age"], ["*"\]\]
*
* @return A copy of the [[TableSource]] that projects its output.
*/
def projectNestedFields(
fields: Array[Int],
nestedFields: Array[Array[String]]): TableSource
}