com.mongodb.spark.rdd.partitioner.MongoPaginateByCountPartitioner.scala Maven / Gradle / Ivy
/*
* Copyright 2016 MongoDB, Inc.
*
* Licensed 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 com.mongodb.spark.rdd.partitioner
import scala.util.{Failure, Success, Try}
import org.bson.BsonDocument
import com.mongodb.client.MongoCollection
import com.mongodb.spark.MongoConnector
import com.mongodb.spark.config.ReadConfig
/**
* The pagination by count partitioner.
*
* Paginates the collection into a maximum number of partitions.
*
* $configurationProperties
*
* - [[partitionKeyProperty partitionKey]], the field to partition the collection by. The field should be indexed and contain unique values.
* Defaults to `_id`.
* - [[numberOfPartitionsProperty numberOfPartitions]], the maximum number of partitions to create. Defaults to `64`.
*
*
* '''Note:''' This can be a expensive operation as it creates 1 cursor for every partition.
*
* @since 1.0
*/
class MongoPaginateByCountPartitioner extends MongoPartitioner with MongoPaginationPartitioner {
private implicit object BsonValueOrdering extends BsonValueOrdering
private val DefaultPartitionKey = "_id"
private val DefaultNumberOfPartitions = "64"
/**
* The partition key property
*/
val partitionKeyProperty = "partitionKey".toLowerCase()
/**
* The number of partitions property
*/
val numberOfPartitionsProperty = "numberOfPartitions".toLowerCase()
/**
* Calculate the Partitions
*
* @param connector the MongoConnector
* @param readConfig the [[com.mongodb.spark.config.ReadConfig]]
* @return the partitions
*/
override def partitions(connector: MongoConnector, readConfig: ReadConfig, pipeline: Array[BsonDocument]): Array[MongoPartition] = {
val matchQuery = PartitionerHelper.matchQuery(pipeline)
Try(connector.withCollectionDo(readConfig, { coll: MongoCollection[BsonDocument] => coll.countDocuments(matchQuery) })) match {
case Success(count) =>
val partitionerOptions = readConfig.partitionerOptions.map(kv => (kv._1.toLowerCase, kv._2))
val partitionKey = partitionerOptions.getOrElse(partitionKeyProperty, DefaultPartitionKey)
val maxNumberOfPartitions = partitionerOptions.getOrElse(numberOfPartitionsProperty, DefaultNumberOfPartitions).toInt
require(maxNumberOfPartitions > 0, "maxNumberOfPartitions must be greater than zero")
val numberOfPartitions = if (count < maxNumberOfPartitions) count else maxNumberOfPartitions
if (count == 0) {
logInfo(s"Empty collection (${readConfig.collectionName}), using a single partition")
MongoSinglePartitioner.partitions(connector, readConfig, pipeline)
} else {
if (count == numberOfPartitions) {
logWarning("Inefficient partitioning, creating a partition per document. Decrease the `numberOfPartitions` property.")
}
val numDocumentsPerPartition = math.floor(count / numberOfPartitions).toInt
val rightHandBoundaries = calculatePartitions(connector, readConfig, partitionKey, count, numDocumentsPerPartition, matchQuery)
val addMinMax = matchQuery.isEmpty
val partitions = PartitionerHelper.createPartitions(partitionKey, rightHandBoundaries, PartitionerHelper.locations(connector),
addMinMax)
if (!addMinMax) PartitionerHelper.setLastBoundaryToLessThanOrEqualTo(partitionKey, partitions)
partitions
}
case Failure(e) =>
logWarning(s"Could not get collection statistics. Server errmsg: ${e.getMessage}")
throw e
}
}
}
case object MongoPaginateByCountPartitioner extends MongoPaginateByCountPartitioner