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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.index
import com.stratio.cassandra.lucene.IndexException
import com.stratio.cassandra.lucene.index.DocumentIterator._
import com.stratio.cassandra.lucene.util.{Logging, TimeCounter, Tracing}
import org.apache.cassandra.utils.CloseableIterator
import org.apache.lucene.document.Document
import org.apache.lucene.index.Term
import org.apache.lucene.search.BooleanClause.Occur._
import org.apache.lucene.search.EarlyTerminatingSortingCollector._
import org.apache.lucene.search._
/** [[CloseableIterator]] for retrieving Lucene documents satisfying a query.
*
* @param cursors the searcher managers and pointers of the involved indexes
* @param indexSort the sort of the index
* @param querySort the sort in which the documents are going to be retrieved
* @param query the query to be satisfied by the documents
* @param limit the iteration page size
* @param fields the names of the document fields to be loaded
* @author Andres de la Pena `[email protected]`
*/
class DocumentIterator(
cursors: List[(SearcherManager, Option[Term])],
indexSort: Sort,
querySort: Sort,
query: Query,
limit: Int,
fields: java.util.Set[String])
extends Iterator[(Document, ScoreDoc)] with AutoCloseable with Logging with Tracing {
private[this] val pageSize = Math.min(limit, MAX_PAGE_SIZE) + 1
private[this] val documents = new java.util.LinkedList[(Document, ScoreDoc)]
private[this] val indices = cursors.indices
private[this] val managers = cursors.map(_._1)
private[this] val searchers = managers.map(_.acquire())
private[this] val afterTerms = cursors.map(_._2)
private[this] val offsets = cursors.map(_ => 0).toArray
private[this] var finished = false
private[this] var closed = false
private[this] def releaseSearchers(): Unit =
indices.foreach(i => managers(i).release(searchers(i)))
/** The sort of the query rewritten by the searcher. */
private[this] val sort = try {
querySort.rewrite(searchers.head)
} catch {
case e: Exception =>
releaseSearchers()
throw new IndexException(e, s"Error rewriting sort $indexSort")
}
/** The start after positions. */
private[this] val afters = try {
indices.map(i => afterTerms(i).map(term => {
val time = TimeCounter.start
val builder = new BooleanQuery.Builder
builder.add(new TermQuery(term), FILTER)
builder.add(query, MUST)
val scores = searchers(i).search(builder.build, 1, sort).scoreDocs
if (scores.nonEmpty) {
tracer.trace("Lucene index seeks last index position")
logger.debug(s"Start position found in $time")
scores.head
} else throw new IndexException("Last page position not found")
})).toArray
} catch {
case e: Exception =>
releaseSearchers()
throw new IndexException(e, "Error while searching for the last page position")
}
private[this] def fetch() = {
try {
val fetchTime = TimeCounter.start
val fieldDocs = indices.map(i => {
val afterTerm = afterTerms(i)
if (afterTerm.isEmpty && canEarlyTerminate(sort, indexSort)) {
val fieldDoc = afters(i).map(_.asInstanceOf[FieldDoc]).orNull
val collect = TopFieldCollector.create(sort, pageSize, fieldDoc, true, false, false)
val hits = offsets(i) + pageSize
val earlyCollect = new EarlyTerminatingSortingCollector(collect, sort, hits, indexSort)
searchers(i).search(query, earlyCollect)
val topDocs = collect.topDocs
offsets(i) += topDocs.scoreDocs.length
topDocs
} else searchers(i).searchAfter(afters(i).orNull, query, pageSize, sort, false, false)
}).toArray
// Merge partitions results
val scoreDocs = TopDocs.merge(sort, pageSize, fieldDocs).scoreDocs
val numFetched = scoreDocs.length
finished = numFetched < pageSize
for (scoreDoc <- scoreDocs) {
val shard = scoreDoc.shardIndex
afters(shard) = Some(scoreDoc)
val document = searchers(shard).doc(scoreDoc.doc, fields)
documents.add((document, scoreDoc))
}
tracer.trace(s"Lucene index fetches $numFetched documents")
logger.debug(s"Page fetched with $numFetched documents in $fetchTime")
} catch {
case e: Exception =>
close()
throw new IndexException(e, s"Error searching with $query and $sort")
}
if (finished) close()
}
/** Returns if more documents should be fetched from the Lucene index.
*
* @return `true` if more documents should be fetched, `false` otherwise
*/
def needsFetch: Boolean = !finished && documents.isEmpty
/** Returns if the iteration has more documents.
*
* @return `true` if the iteration has more documents, `false` otherwise
*/
override def hasNext: Boolean = {
if (needsFetch) fetch()
!documents.isEmpty
}
/** Returns the next document-score tuple in the iteration.
*
* @return the next document-score tuple
* @throws NoSuchElementException if the iteration has no more documents
*/
override def next: (Document, ScoreDoc) = {
if (hasNext) documents.poll else throw new NoSuchElementException
}
/** Closes the [[IndexSearcher]] and any other resources */
override def close(): Unit = {
if (!closed) try releaseSearchers() finally closed = true
}
}
/** Companion object for [[DocumentIterator]]. */
object DocumentIterator {
/** The max number of rows to be read per iteration. */
val MAX_PAGE_SIZE = 10000
}
