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/*
* 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 java.util
import scala.collection.JavaConverters._
import scala.util.{Failure, Success, Try}
import org.bson.{BsonDocument, BsonInt64}
import com.mongodb.MongoCommandException
import com.mongodb.client.MongoCollection
import com.mongodb.client.model.{Aggregates, Projections, Sorts}
import com.mongodb.spark.MongoConnector
import com.mongodb.spark.config.ReadConfig
/**
* The Sample Partitioner.
*
* Uses the average document size and random sampling of the collection to determine suitable partitions for the collection.
*
* $configurationProperties
*
* - [[partitionKeyProperty partitionKey]], the field to partition the collection by. The field should be indexed and contain unique values.
* Defaults to `_id`.
* - [[partitionSizeMBProperty partitionSizeMB]], the size (in MB) for each partition. Defaults to `64`.
* - [[samplesPerPartitionProperty samplesPerPartition]], the number of samples for each partition. Defaults to `10`.
*
* *Note:* Requires MongoDB 3.2+
* *Note:* Does not support views. Use `MongoPaginateByCountPartitioner` or create a custom partitioner.
*
* @since 1.0
*/
class MongoSamplePartitioner extends MongoPartitioner {
private val DefaultPartitionKey = "_id"
private val DefaultPartitionSizeMB = "64"
private val DefaultSamplesPerPartition = "10"
/**
* The partition key property
*/
val partitionKeyProperty = "partitionKey".toLowerCase()
/**
* The partition size MB property
*/
val partitionSizeMBProperty = "partitionSizeMB".toLowerCase()
/**
* The number of samples for each partition
*/
val samplesPerPartitionProperty = "samplesPerPartition".toLowerCase()
/**
* Calculate the Partitions
*
* @param connector the MongoConnector
* @param readConfig the [[com.mongodb.spark.config.ReadConfig]]
* @return the partitions
*/
// scalastyle:off cyclomatic.complexity
override def partitions(connector: MongoConnector, readConfig: ReadConfig, pipeline: Array[BsonDocument]): Array[MongoPartition] = {
Try(PartitionerHelper.collStats(connector, readConfig)) match {
case Success(results) =>
val matchQuery = PartitionerHelper.matchQuery(pipeline)
val partitionerOptions = readConfig.partitionerOptions.map(kv => (kv._1.toLowerCase, kv._2))
val partitionKey = partitionerOptions.getOrElse(partitionKeyProperty, DefaultPartitionKey)
val partitionSizeInBytes = partitionerOptions.getOrElse(partitionSizeMBProperty, DefaultPartitionSizeMB).toInt * 1024 * 1024
val samplesPerPartition = partitionerOptions.getOrElse(samplesPerPartitionProperty, DefaultSamplesPerPartition).toInt
val count = if (matchQuery.isEmpty) {
results.getNumber("count").longValue()
} else {
connector.withCollectionDo(readConfig, { coll: MongoCollection[BsonDocument] => coll.countDocuments(matchQuery) })
}
val avgObjSizeInBytes = results.get("avgObjSize", new BsonInt64(0)).asNumber().longValue()
val numDocumentsPerPartition: Int = math.floor(partitionSizeInBytes.toFloat / avgObjSizeInBytes).toInt
val numberOfSamples = math.floor(samplesPerPartition * count / numDocumentsPerPartition.toFloat).toInt
if (numDocumentsPerPartition >= count) {
MongoSinglePartitioner.partitions(connector, readConfig, pipeline)
} else {
val samples = connector.withCollectionDo(readConfig, {
coll: MongoCollection[BsonDocument] =>
coll.aggregate(List(
Aggregates.`match`(matchQuery),
Aggregates.sample(numberOfSamples),
Aggregates.project(Projections.include(partitionKey)),
Aggregates.sort(Sorts.ascending(partitionKey))
).asJava).allowDiskUse(true).into(new util.ArrayList[BsonDocument]()).asScala
})
def collectSplit(i: Int): Boolean = (i % samplesPerPartition == 0) || !matchQuery.isEmpty && i == count - 1
val rightHandBoundaries = samples.zipWithIndex.collect {
case (field, i) if collectSplit(i) => field.get(partitionKey)
}
PartitionerHelper.createPartitions(partitionKey, rightHandBoundaries, PartitionerHelper.locations(connector))
}
case Failure(ex: MongoCommandException) if ex.getErrorMessage.endsWith("not found.") || ex.getErrorCode == 26 =>
logInfo(s"Could not find collection (${readConfig.collectionName}), using a single partition")
MongoSinglePartitioner.partitions(connector, readConfig, pipeline)
case Failure(e) =>
logWarning(s"Could not get collection statistics. Server errmsg: ${e.getMessage}")
throw e
}
}
// scalastyle:on cyclomatic.complexity
}
case object MongoSamplePartitioner extends MongoSamplePartitioner
