romseygeek commented on a change in pull request #1440: URL: https://github.com/apache/lucene-solr/pull/1440#discussion_r412829154
########## File path: lucene/core/src/java/org/apache/lucene/index/IndexSorter.java ########## @@ -0,0 +1,500 @@ +/* + * 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.lucene.index; + +import java.io.IOException; +import java.util.Arrays; +import java.util.Comparator; +import java.util.List; + +import org.apache.lucene.search.FieldComparator; +import org.apache.lucene.search.SortField; +import org.apache.lucene.store.DataInput; +import org.apache.lucene.store.DataOutput; +import org.apache.lucene.util.LongValues; +import org.apache.lucene.util.NumericUtils; +import org.apache.lucene.util.packed.PackedInts; + +import static org.apache.lucene.search.DocIdSetIterator.NO_MORE_DOCS; + +/** + * Handles how documents should be sorted in an index, both within a segment and between + * segments. + * + * Implementers must provide the following methods: + * {@link #getDocComparator(LeafReader)} - an object that determines how documents within a segment are to be sorted + * {@link #getComparableProviders(List)} - an array of objects that return a sortable long value per document and segment + * {@link #serialize(DataOutput)} - how the sort should be written into the segment header + * {@link #getProviderName()} - the SPI-registered name of a {@link SortFieldProvider} to deserialize the sort + * + * The companion {@link SortFieldProvider} should be registered with SPI via {@code META-INF/services} + */ +public interface IndexSorter { + + /** Used for sorting documents across segments */ + public interface ComparableProvider { + /** + * Returns a long so that the natural ordering of long values matches the + * ordering of doc IDs for the given comparator + */ + long getAsComparableLong(int docID) throws IOException; + } + + /** A comparator of doc IDs, used for sorting documents within a segment */ + public interface DocComparator { + /** Compare docID1 against docID2. The contract for the return value is the + * same as {@link Comparator#compare(Object, Object)}. */ + int compare(int docID1, int docID2); + } + + /** + * Get an array of {@link ComparableProvider}, one per segment, for merge sorting documents in different segments + * @param readers the readers to be merged + */ + public abstract ComparableProvider[] getComparableProviders(List<? extends LeafReader> readers) throws IOException; + + /** + * Get a comparator that determines the sort order of docs within a single Reader. + * + * NB We cannot simply use the {@link FieldComparator} API because it requires docIDs to be sent + * in-order. The default implementations allocate array[maxDoc] to hold native values for comparison, + * but 1) they are transient (only alive while sorting this one segment) and 2) in the typical + * index sorting case, they are only used to sort newly flushed segments, which will be smaller + * than merged segments + * + * @param reader the Reader to sort + */ + public abstract DocComparator getDocComparator(LeafReader reader) throws IOException; + + /** + * Serializes the parent SortField. This is used to write Sort information into the Segment header + * + * @see SortFieldProvider#loadSortField(DataInput) + */ + public abstract void serialize(DataOutput out) throws IOException; + + /** + * The SPI-registered name of a {@link SortFieldProvider} that will deserialize the parent SortField + */ + public abstract String getProviderName(); + + /** + * Provide a NumericDocValues instance for a LeafReader + */ + public interface NumericDocValuesProvider { + /** + * Returns the NumericDocValues instance for this LeafReader + */ + NumericDocValues get(LeafReader reader) throws IOException; + } + + /** + * Provide a SortedDocValues instance for a LeafReader + */ + public interface SortedDocValuesProvider { + /** + * Returns the SortedDocValues instance for this LeafReader + */ + SortedDocValues get(LeafReader reader) throws IOException; + } + + /** + * Serialize an object into a DataOutput + */ + public interface Serializer { + /** Serializes an object into a DataOutput */ + void serialize(DataOutput out) throws IOException; + } + + /** + * Sorts documents based on integer values from a NumericDocValues instance + */ + public static final class IntSorter implements IndexSorter { Review comment: IndexSorter is an interface (started as an abstract class in a first iteration) so everything is public and static, and we don't need those modifiers anymore. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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