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/*
* Copyright (C) 2014 Stratio (http://stratio.com)
*
* 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.stratio.cassandra.lucene
import java.util.Collections
import java.util.function.BiFunction
import com.stratio.cassandra.lucene.IndexPostProcessor._
import com.stratio.cassandra.lucene.index.RAMIndex
import com.stratio.cassandra.lucene.search.Search
import com.stratio.cassandra.lucene.util._
import org.apache.cassandra.db.SinglePartitionReadCommand.Group
import org.apache.cassandra.db.partitions.PartitionIterator
import org.apache.cassandra.db.rows.Row
import org.apache.cassandra.db.{DecoratedKey, ReadCommand, ReadQuery, SinglePartitionReadCommand}
import org.apache.lucene.document.{Document, StoredField}
import scala.collection.JavaConverters._
import scala.collection.mutable
/** Post processes in the coordinator node the results of a distributed search. In other words,
* gets the k globally best results from all the k best node-local results.
*
* @param service the index service
* @author Andres de la Pena `[email protected]`
*/
sealed abstract class IndexPostProcessor[A <: ReadQuery](service: IndexService)
extends BiFunction[PartitionIterator, A, PartitionIterator] with Logging with Tracing {
/** Returns a partition iterator containing the top-k rows of the specified partition iterator
* according to the specified search.
*
* @param partitions a partition iterator
* @param search a search defining the ordering
* @param limit the number of results to be returned
* @param now the operation time in seconds
* @return
*/
protected def process(partitions: PartitionIterator, search: Search, limit: Int, now: Int)
: PartitionIterator = {
if (search.requiresFullScan) {
val rows = collect(partitions)
if (search.requiresPostProcessing && rows.nonEmpty) {
return top(rows, search, limit, now)
}
}
partitions
}
/** Collects the rows of the specified partition iterator. The iterator gets traversed after this
* operation so it can't be reused.
*
* @param partitions a partition iterator
* @return the rows contained in the partition iterator
*/
private def collect(partitions: PartitionIterator): List[(DecoratedKey, SingleRowIterator)] = {
val time = TimeCounter.start
val rows = mutable.ListBuffer[(DecoratedKey, SingleRowIterator)]()
for (partition <- partitions.asScala) {
try {
val key = partition.partitionKey
while (partition.hasNext) {
rows += ((key, new SingleRowIterator(partition)))
}
} finally partition.close()
}
logger.debug(s"Collected ${rows.size} rows in $time")
rows.toList
}
/** Takes the k best rows of the specified rows according to the specified search.
*
* @param rows the rows to be sorted
* @param search a search defining the ordering
* @param limit the number of results to be returned
* @param now the operation time in seconds
* @return
*/
private def top(
rows: List[(DecoratedKey, SingleRowIterator)],
search: Search,
limit: Int,
now: Int): PartitionIterator = {
val time = TimeCounter.start
val index = new RAMIndex(service.schema.analyzer)
try {
// Index collected rows in memory
for (id <- rows.indices) {
val (key, rowIterator) = rows(id)
val row = rowIterator.row
val doc = document(key, row, search, now)
doc.add(new StoredField(ID_FIELD, id)) // Mark document
index.add(doc)
}
// Repeat search to sort partial results
val query = search.postProcessingQuery(service.schema)
val sort = service.sort(search)
val docs = index.search(query, sort, limit, FIELDS_TO_LOAD)
// Collect and decorate
val merged = for ((doc, score) <- docs) yield {
val id = doc.get(ID_FIELD).toInt
val rowIterator = rows(id)._2
rowIterator.decorated(row => service.expressionMapper.decorate(row, score, now))
}
tracer.trace(s"Lucene post-process ${rows.size} collected rows to ${merged.size} rows")
logger.debug(s"Post-processed ${rows.size} rows to ${merged.size} rows in $time")
new SimplePartitionIterator(merged)
} finally index.close()
}
/** Returns a [[Document]] representing the specified row with only the fields required to satisfy
* the specified [[Search]].
*
* @param key a partition key
* @param row a row
* @param search a search
* @return a document with just the fields required to satisfy the search
*/
private def document(key: DecoratedKey, row: Row, search: Search, now: Int): Document = {
val document = new Document
val clustering = row.clustering()
val columns = service.columnsMapper.columns(key, row, now)
service.keyIndexableFields(key, clustering).foreach(document.add)
service.schema.postProcessingIndexableFields(columns, search).forEach(document add _)
document
}
}
/** Companion object for [[IndexPostProcessor]]. */
object IndexPostProcessor {
val ID_FIELD = "_id"
val FIELDS_TO_LOAD: java.util.Set[String] = Collections.singleton(ID_FIELD)
}
/** An [[IndexPostProcessor]] for [[ReadCommand]]s.
*
* @param service the index service
* @author Andres de la Pena `[email protected]`
*/
class ReadCommandPostProcessor(service: IndexService)
extends IndexPostProcessor[ReadCommand](service) {
/** @inheritdoc */
override def apply(partitions: PartitionIterator, command: ReadCommand): PartitionIterator = {
if (!partitions.hasNext || command.isInstanceOf[SinglePartitionReadCommand]) return partitions
val search = service.expressionMapper.search(command)
process(partitions, search, command.limits.count, command.nowInSec)
}
}
/** An [[IndexPostProcessor]] for [[Group]] commands.
*
* @param service the index service
* @author Andres de la Pena `[email protected]`
*/
class GroupPostProcessor(service: IndexService) extends IndexPostProcessor[Group](service) {
/** @inheritdoc */
override def apply(partitions: PartitionIterator, group: Group): PartitionIterator = {
if (!partitions.hasNext || group.commands.size <= 1) return partitions
val search = service.expressionMapper.search(group.commands.get(0))
process(partitions, search, group.limits.count, group.nowInSec)
}
}
