read/streaming/Offset.java

0001 /*
0002  * Licensed to the Apache Software Foundation (ASF) under one or more
0003  * contributor license agreements.  See the NOTICE file distributed with
0004  * this work for additional information regarding copyright ownership.
0005  * The ASF licenses this file to You under the Apache License, Version 2.0
0006  * (the "License"); you may not use this file except in compliance with
0007  * the License.  You may obtain a copy of the License at
0008  *
0009  *    http://www.apache.org/licenses/LICENSE-2.0
0010  *
0011  * Unless required by applicable law or agreed to in writing, software
0012  * distributed under the License is distributed on an "AS IS" BASIS,
0013  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
0014  * See the License for the specific language governing permissions and
0015  * limitations under the License.
0016  */
0017
0018 package org.apache.spark.sql.connector.read.streaming;
0019
0020 import org.apache.spark.annotation.Evolving;
0021
0022 /**
0023  * An abstract representation of progress through a {@link MicroBatchStream} or
0024  * {@link ContinuousStream}.
0025  * During execution, offsets provided by the data source implementation will be logged and used as
0026  * restart checkpoints. Each source should provide an offset implementation which the source can use
0027  * to reconstruct a position in the stream up to which data has been seen/processed.
0028  *
0029  * @since 3.0.0
0030  */
0031 @Evolving
0032 public abstract class Offset {
0033     /**
0034      * A JSON-serialized representation of an Offset that is
0035      * used for saving offsets to the offset log.
0036      * Note: We assume that equivalent/equal offsets serialize to
0037      * identical JSON strings.
0038      *
0039      * @return JSON string encoding
0040      */
0041     public abstract String json();
0042
0043     /**
0044      * Equality based on JSON string representation. We leverage the
0045      * JSON representation for normalization between the Offset's
0046      * in deserialized and serialized representations.
0047      */
0048     @Override
0049     public boolean equals(Object obj) {
0050         if (obj instanceof Offset) {
0051             return this.json().equals(((Offset) obj).json());
0052         } else {
0053             return false;
0054         }
0055     }
0056
0057     @Override
0058     public int hashCode() {
0059         return this.json().hashCode();
0060     }
0061
0062     @Override
0063     public String toString() {
0064         return this.json();
0065     }
0066 }