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/*
* 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.api;
import org.apache.flink.annotation.PublicEvolving;
import org.apache.flink.table.expressions.Expression;
import java.util.Arrays;
/**
* Helper class for creating an over window. Similar to SQL, over window aggregates compute an
* aggregate for each input row over a range of its neighboring rows.
*
* Java Example:
*
*
{@code
* Over.partitionBy("a").orderBy("rowtime").preceding("unbounded_range").as("w")
* }
*
* Scala Example:
*
*
{@code
* Over partitionBy 'a orderBy 'rowtime preceding UNBOUNDED_RANGE as 'w
* }
*/
@PublicEvolving
public final class Over {
/**
* Partitions the elements on some partition keys.
*
* Each partition is individually sorted and aggregate functions are applied to each
* partition separately.
*
* @param partitionBy list of field references
* @return an over window with defined partitioning
*/
public static OverWindowPartitioned partitionBy(Expression... partitionBy) {
return new OverWindowPartitioned(Arrays.asList(partitionBy));
}
/**
* Specifies the time attribute on which rows are ordered.
*
*
For streaming tables, reference a rowtime or proctime time attribute here to specify the
* time mode.
*
*
For batch tables, refer to a timestamp or long attribute.
*
* @param orderBy field reference
* @return an over window with defined order
*/
public static OverWindowPartitionedOrdered orderBy(Expression orderBy) {
return partitionBy().orderBy(orderBy);
}
}