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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.spark.sql.execution.streaming
/**
* A general MetadataLog that supports the following features:
*
* - Allow the user to store a metadata object for each batch.
* - Allow the user to query the latest batch id.
* - Allow the user to query the metadata object of a specified batch id.
* - Allow the user to query metadata objects in a range of batch ids.
* - Allow the user to remove obsolete metadata
*/
trait MetadataLog[T] {
/**
* Store the metadata for the specified batchId and return `true` if successful. If the batchId's
* metadata has already been stored, this method will return `false`.
*/
def add(batchId: Long, metadata: T): Boolean
/**
* Return the metadata for the specified batchId if it's stored. Otherwise, return None.
*/
def get(batchId: Long): Option[T]
/**
* Return metadata for batches between startId (inclusive) and endId (inclusive). If `startId` is
* `None`, just return all batches before endId (inclusive).
*/
def get(startId: Option[Long], endId: Option[Long]): Array[(Long, T)]
/**
* Return the latest batch Id and its metadata if exist.
*/
def getLatest(): Option[(Long, T)]
/**
* Removes all the log entry earlier than thresholdBatchId (exclusive).
* This operation should be idempotent.
*/
def purge(thresholdBatchId: Long): Unit
}
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