| /* |
| * 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.FileNotFoundException; |
| import java.io.IOException; |
| import java.nio.file.NoSuchFileException; |
| import java.util.ArrayList; |
| import java.util.Collections; |
| import java.util.List; |
| import org.apache.lucene.search.SearcherManager; // javadocs |
| import org.apache.lucene.store.Directory; |
| |
| /** |
| * DirectoryReader is an implementation of {@link CompositeReader} that can read indexes in a {@link |
| * Directory}. |
| * |
| * <p>DirectoryReader instances are usually constructed with a call to one of the static <code> |
| * open()</code> methods, e.g. {@link #open(Directory)}. |
| * |
| * <p>For efficiency, in this API documents are often referred to via <i>document numbers</i>, |
| * non-negative integers which each name a unique document in the index. These document numbers are |
| * ephemeral -- they may change as documents are added to and deleted from an index. Clients should |
| * thus not rely on a given document having the same number between sessions. |
| * |
| * <p><a id="thread-safety"></a> |
| * |
| * <p><b>NOTE</b>: {@link IndexReader} instances are completely thread safe, meaning multiple |
| * threads can call any of its methods, concurrently. If your application requires external |
| * synchronization, you should <b>not</b> synchronize on the <code>IndexReader</code> instance; use |
| * your own (non-Lucene) objects instead. |
| */ |
| public abstract class DirectoryReader extends BaseCompositeReader<LeafReader> { |
| |
| /** The index directory. */ |
| protected final Directory directory; |
| |
| /** |
| * Returns a IndexReader reading the index in the given Directory |
| * |
| * @param directory the index directory |
| * @throws IOException if there is a low-level IO error |
| */ |
| public static DirectoryReader open(final Directory directory) throws IOException { |
| return StandardDirectoryReader.open(directory, null); |
| } |
| |
| /** |
| * Open a near real time IndexReader from the {@link org.apache.lucene.index.IndexWriter}. |
| * |
| * @param writer The IndexWriter to open from |
| * @return The new IndexReader |
| * @throws CorruptIndexException if the index is corrupt |
| * @throws IOException if there is a low-level IO error |
| * @see #openIfChanged(DirectoryReader,IndexWriter,boolean) |
| * @lucene.experimental |
| */ |
| public static DirectoryReader open(final IndexWriter writer) throws IOException { |
| return open(writer, true, false); |
| } |
| |
| /** |
| * Expert: open a near real time IndexReader from the {@link org.apache.lucene.index.IndexWriter}, |
| * controlling whether past deletions should be applied. |
| * |
| * @param writer The IndexWriter to open from |
| * @param applyAllDeletes If true, all buffered deletes will be applied (made visible) in the |
| * returned reader. If false, the deletes are not applied but remain buffered (in IndexWriter) |
| * so that they will be applied in the future. Applying deletes can be costly, so if your app |
| * can tolerate deleted documents being returned you might gain some performance by passing |
| * false. |
| * @param writeAllDeletes If true, new deletes will be written down to index files instead of |
| * carried over from writer to reader directly in heap |
| * @see #open(IndexWriter) |
| * @lucene.experimental |
| */ |
| public static DirectoryReader open( |
| final IndexWriter writer, boolean applyAllDeletes, boolean writeAllDeletes) |
| throws IOException { |
| return writer.getReader(applyAllDeletes, writeAllDeletes); |
| } |
| |
| /** |
| * Expert: returns an IndexReader reading the index in the given {@link IndexCommit}. |
| * |
| * @param commit the commit point to open |
| * @throws IOException if there is a low-level IO error |
| */ |
| public static DirectoryReader open(final IndexCommit commit) throws IOException { |
| return StandardDirectoryReader.open(commit.getDirectory(), commit); |
| } |
| |
| /** |
| * Expert: returns an IndexReader reading the index on the given {@link IndexCommit}. This method |
| * allows to open indices that were created wih a Lucene version older than N-1 provided that all |
| * codecs for this index are available in the classpath and the segment file format used was |
| * created with Lucene 7 or newer. Users of this API must be aware that Lucene doesn't guarantee |
| * semantic compatibility for indices created with versions older than N-1. All backwards |
| * compatibility aside from the file format is optional and applied on a best effort basis. |
| * |
| * @param commit the commit point to open |
| * @param minSupportedMajorVersion the minimum supported major index version |
| * @throws IOException if there is a low-level IO error |
| */ |
| public static DirectoryReader open(final IndexCommit commit, int minSupportedMajorVersion) |
| throws IOException { |
| return StandardDirectoryReader.open(commit.getDirectory(), minSupportedMajorVersion, commit); |
| } |
| |
| /** |
| * If the index has changed since the provided reader was opened, open and return a new reader; |
| * else, return null. The new reader, if not null, will be the same type of reader as the previous |
| * one, ie an NRT reader will open a new NRT reader, a MultiReader will open a new MultiReader, |
| * etc. |
| * |
| * <p>This method is typically far less costly than opening a fully new <code>DirectoryReader |
| * </code> as it shares resources (for example sub-readers) with the provided <code> |
| * DirectoryReader</code>, when possible. |
| * |
| * <p>The provided reader is not closed (you are responsible for doing so); if a new reader is |
| * returned you also must eventually close it. Be sure to never close a reader while other threads |
| * are still using it; see {@link SearcherManager} to simplify managing this. |
| * |
| * @throws CorruptIndexException if the index is corrupt |
| * @throws IOException if there is a low-level IO error |
| * @return null if there are no changes; else, a new DirectoryReader instance which you must |
| * eventually close |
| */ |
| public static DirectoryReader openIfChanged(DirectoryReader oldReader) throws IOException { |
| final DirectoryReader newReader = oldReader.doOpenIfChanged(); |
| assert newReader != oldReader; |
| return newReader; |
| } |
| |
| /** |
| * If the IndexCommit differs from what the provided reader is searching, open and return a new |
| * reader; else, return null. |
| * |
| * @see #openIfChanged(DirectoryReader) |
| */ |
| public static DirectoryReader openIfChanged(DirectoryReader oldReader, IndexCommit commit) |
| throws IOException { |
| final DirectoryReader newReader = oldReader.doOpenIfChanged(commit); |
| assert newReader != oldReader; |
| return newReader; |
| } |
| |
| /** |
| * Expert: If there changes (committed or not) in the {@link IndexWriter} versus what the provided |
| * reader is searching, then open and return a new IndexReader searching both committed and |
| * uncommitted changes from the writer; else, return null (though, the current implementation |
| * never returns null). |
| * |
| * <p>This provides "near real-time" searching, in that changes made during an {@link IndexWriter} |
| * session can be quickly made available for searching without closing the writer nor calling |
| * {@link IndexWriter#commit}. |
| * |
| * <p>It's <i>near</i> real-time because there is no hard guarantee on how quickly you can get a |
| * new reader after making changes with IndexWriter. You'll have to experiment in your situation |
| * to determine if it's fast enough. As this is a new and experimental feature, please report back |
| * on your findings so we can learn, improve and iterate. |
| * |
| * <p>The very first time this method is called, this writer instance will make every effort to |
| * pool the readers that it opens for doing merges, applying deletes, etc. This means additional |
| * resources (RAM, file descriptors, CPU time) will be consumed. |
| * |
| * <p>For lower latency on reopening a reader, you should call {@link |
| * IndexWriterConfig#setMergedSegmentWarmer} to pre-warm a newly merged segment before it's |
| * committed to the index. This is important for minimizing index-to-search delay after a large |
| * merge. |
| * |
| * <p>If an addIndexes* call is running in another thread, then this reader will only search those |
| * segments from the foreign index that have been successfully copied over, so far. |
| * |
| * <p><b>NOTE</b>: Once the writer is closed, any outstanding readers may continue to be used. |
| * However, if you attempt to reopen any of those readers, you'll hit an {@link |
| * org.apache.lucene.store.AlreadyClosedException}. |
| * |
| * @return DirectoryReader that covers entire index plus all changes made so far by this |
| * IndexWriter instance, or null if there are no new changes |
| * @param writer The IndexWriter to open from |
| * @throws IOException if there is a low-level IO error |
| * @lucene.experimental |
| */ |
| public static DirectoryReader openIfChanged(DirectoryReader oldReader, IndexWriter writer) |
| throws IOException { |
| return openIfChanged(oldReader, writer, true); |
| } |
| |
| /** |
| * Expert: Opens a new reader, if there are any changes, controlling whether past deletions should |
| * be applied. |
| * |
| * @see #openIfChanged(DirectoryReader,IndexWriter) |
| * @param writer The IndexWriter to open from |
| * @param applyAllDeletes If true, all buffered deletes will be applied (made visible) in the |
| * returned reader. If false, the deletes are not applied but remain buffered (in IndexWriter) |
| * so that they will be applied in the future. Applying deletes can be costly, so if your app |
| * can tolerate deleted documents being returned you might gain some performance by passing |
| * false. |
| * @throws IOException if there is a low-level IO error |
| * @lucene.experimental |
| */ |
| public static DirectoryReader openIfChanged( |
| DirectoryReader oldReader, IndexWriter writer, boolean applyAllDeletes) throws IOException { |
| final DirectoryReader newReader = oldReader.doOpenIfChanged(writer, applyAllDeletes); |
| assert newReader != oldReader; |
| return newReader; |
| } |
| |
| /** |
| * Returns all commit points that exist in the Directory. Normally, because the default is {@link |
| * KeepOnlyLastCommitDeletionPolicy}, there would be only one commit point. But if you're using a |
| * custom {@link IndexDeletionPolicy} then there could be many commits. Once you have a given |
| * commit, you can open a reader on it by calling {@link DirectoryReader#open(IndexCommit)} There |
| * must be at least one commit in the Directory, else this method throws {@link |
| * IndexNotFoundException}. Note that if a commit is in progress while this method is running, |
| * that commit may or may not be returned. |
| * |
| * @return a sorted list of {@link IndexCommit}s, from oldest to latest. |
| */ |
| public static List<IndexCommit> listCommits(Directory dir) throws IOException { |
| final String[] files = dir.listAll(); |
| |
| List<IndexCommit> commits = new ArrayList<>(); |
| |
| SegmentInfos latest = SegmentInfos.readLatestCommit(dir, 0); |
| final long currentGen = latest.getGeneration(); |
| |
| commits.add(new StandardDirectoryReader.ReaderCommit(null, latest, dir)); |
| |
| for (int i = 0; i < files.length; i++) { |
| |
| final String fileName = files[i]; |
| |
| if (fileName.startsWith(IndexFileNames.SEGMENTS) |
| && SegmentInfos.generationFromSegmentsFileName(fileName) < currentGen) { |
| |
| SegmentInfos sis = null; |
| try { |
| // IOException allowed to throw there, in case |
| // segments_N is corrupt |
| sis = SegmentInfos.readCommit(dir, fileName, 0); |
| } catch (FileNotFoundException | NoSuchFileException fnfe) { |
| // LUCENE-948: on NFS (and maybe others), if |
| // you have writers switching back and forth |
| // between machines, it's very likely that the |
| // dir listing will be stale and will claim a |
| // file segments_X exists when in fact it |
| // doesn't. So, we catch this and handle it |
| // as if the file does not exist |
| } |
| |
| if (sis != null) { |
| commits.add(new StandardDirectoryReader.ReaderCommit(null, sis, dir)); |
| } |
| } |
| } |
| |
| // Ensure that the commit points are sorted in ascending order. |
| Collections.sort(commits); |
| |
| return commits; |
| } |
| |
| /** |
| * Returns <code>true</code> if an index likely exists at the specified directory. Note that if a |
| * corrupt index exists, or if an index in the process of committing |
| * |
| * @param directory the directory to check for an index |
| * @return <code>true</code> if an index exists; <code>false</code> otherwise |
| */ |
| public static boolean indexExists(Directory directory) throws IOException { |
| // LUCENE-2812, LUCENE-2727, LUCENE-4738: this logic will |
| // return true in cases that should arguably be false, |
| // such as only IW.prepareCommit has been called, or a |
| // corrupt first commit, but it's too deadly to make |
| // this logic "smarter" and risk accidentally returning |
| // false due to various cases like file description |
| // exhaustion, access denied, etc., because in that |
| // case IndexWriter may delete the entire index. It's |
| // safer to err towards "index exists" than try to be |
| // smart about detecting not-yet-fully-committed or |
| // corrupt indices. This means that IndexWriter will |
| // throw an exception on such indices and the app must |
| // resolve the situation manually: |
| String[] files = directory.listAll(); |
| |
| String prefix = IndexFileNames.SEGMENTS + "_"; |
| for (String file : files) { |
| if (file.startsWith(prefix)) { |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| /** |
| * Expert: Constructs a {@code DirectoryReader} on the given subReaders. |
| * |
| * @param segmentReaders the wrapped atomic index segment readers. This array is returned by |
| * {@link #getSequentialSubReaders} and used to resolve the correct subreader for docID-based |
| * methods. <b>Please note:</b> This array is <b>not</b> cloned and not protected for |
| * modification outside of this reader. Subclasses of {@code DirectoryReader} should take care |
| * to not allow modification of this internal array, e.g. {@link #doOpenIfChanged()}. |
| */ |
| protected DirectoryReader(Directory directory, LeafReader[] segmentReaders) throws IOException { |
| super(segmentReaders); |
| this.directory = directory; |
| } |
| |
| /** Returns the directory this index resides in. */ |
| public final Directory directory() { |
| // Don't ensureOpen here -- in certain cases, when a |
| // cloned/reopened reader needs to commit, it may call |
| // this method on the closed original reader |
| return directory; |
| } |
| |
| /** |
| * Implement this method to support {@link #openIfChanged(DirectoryReader)}. If this reader does |
| * not support reopen, return {@code null}, so client code is happy. This should be consistent |
| * with {@link #isCurrent} (should always return {@code true}) if reopen is not supported. |
| * |
| * @throws IOException if there is a low-level IO error |
| * @return null if there are no changes; else, a new DirectoryReader instance. |
| */ |
| protected abstract DirectoryReader doOpenIfChanged() throws IOException; |
| |
| /** |
| * Implement this method to support {@link #openIfChanged(DirectoryReader,IndexCommit)}. If this |
| * reader does not support reopen from a specific {@link IndexCommit}, throw {@link |
| * UnsupportedOperationException}. |
| * |
| * @throws IOException if there is a low-level IO error |
| * @return null if there are no changes; else, a new DirectoryReader instance. |
| */ |
| protected abstract DirectoryReader doOpenIfChanged(final IndexCommit commit) throws IOException; |
| |
| /** |
| * Implement this method to support {@link #openIfChanged(DirectoryReader,IndexWriter,boolean)}. |
| * If this reader does not support reopen from {@link IndexWriter}, throw {@link |
| * UnsupportedOperationException}. |
| * |
| * @throws IOException if there is a low-level IO error |
| * @return null if there are no changes; else, a new DirectoryReader instance. |
| */ |
| protected abstract DirectoryReader doOpenIfChanged(IndexWriter writer, boolean applyAllDeletes) |
| throws IOException; |
| |
| /** |
| * Version number when this IndexReader was opened. |
| * |
| * <p>This method returns the version recorded in the commit that the reader opened. This version |
| * is advanced every time a change is made with {@link IndexWriter}. |
| */ |
| public abstract long getVersion(); |
| |
| /** |
| * Check whether any new changes have occurred to the index since this reader was opened. |
| * |
| * <p>If this reader was created by calling {@link #open}, then this method checks if any further |
| * commits (see {@link IndexWriter#commit}) have occurred in the directory. |
| * |
| * <p>If instead this reader is a near real-time reader (ie, obtained by a call to {@link |
| * DirectoryReader#open(IndexWriter)}, or by calling {@link #openIfChanged} on a near real-time |
| * reader), then this method checks if either a new commit has occurred, or any new uncommitted |
| * changes have taken place via the writer. Note that even if the writer has only performed |
| * merging, this method will still return false. |
| * |
| * <p>In any event, if this returns false, you should call {@link #openIfChanged} to get a new |
| * reader that sees the changes. |
| * |
| * @throws IOException if there is a low-level IO error |
| */ |
| public abstract boolean isCurrent() throws IOException; |
| |
| /** |
| * Expert: return the IndexCommit that this reader has opened. |
| * |
| * @lucene.experimental |
| */ |
| public abstract IndexCommit getIndexCommit() throws IOException; |
| } |