/
Impulse.java
55 lines (51 loc) · 2.01 KB
/
Impulse.java
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
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.beam.sdk.transforms;
import org.apache.beam.sdk.annotations.Internal;
import org.apache.beam.sdk.coders.ByteArrayCoder;
import org.apache.beam.sdk.io.Read;
import org.apache.beam.sdk.transforms.windowing.GlobalWindow;
import org.apache.beam.sdk.values.PBegin;
import org.apache.beam.sdk.values.PCollection;
import org.apache.beam.sdk.values.PCollection.IsBounded;
import org.apache.beam.sdk.values.WindowingStrategy;
/**
* <b><i>For internal use only; no backwards-compatibility guarantees.</i></b>
*
* <p>A {@link PTransform} which produces a single empty byte array at the minimum timestamp in the
* {@link GlobalWindow}.
*
* <p>Users should instead use {@link Create} or another {@link Read} transform to begin consuming
* elements.
*/
@Internal
public class Impulse extends PTransform<PBegin, PCollection<byte[]>> {
/** Create a new {@link Impulse} {@link PTransform}. */
public static Impulse create() {
return new Impulse();
}
private Impulse() {}
@Override
public PCollection<byte[]> expand(PBegin input) {
return PCollection.createPrimitiveOutputInternal(
input.getPipeline(),
WindowingStrategy.globalDefault(),
IsBounded.BOUNDED,
ByteArrayCoder.of());
}
}