package org.apache.lucene.index;
/**
* 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.
*/
import java.io.IOException;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.BufferedIndexInput;
import org.apache.lucene.util.cache.Cache;
import org.apache.lucene.util.cache.SimpleLRUCache;
import org.apache.lucene.util.CloseableThreadLocal;
/** This stores a monotonically increasing set of <Term, TermInfo> pairs in a
* Directory. Pairs are accessed either by Term or by ordinal position the
* set. */
final class TermInfosReader {
private Directory directory;
private String segment;
private FieldInfos fieldInfos;
private CloseableThreadLocal threadResources = new CloseableThreadLocal();
private SegmentTermEnum origEnum;
private long size;
private Term[] indexTerms = null;
private TermInfo[] indexInfos;
private long[] indexPointers;
private SegmentTermEnum indexEnum;
private int indexDivisor = 1;
private int totalIndexInterval;
private final static int DEFAULT_CACHE_SIZE = 1024;
/**
* Per-thread resources managed by ThreadLocal
*/
private static final class ThreadResources {
SegmentTermEnum termEnum;
// Used for caching the least recently looked-up Terms
Cache termInfoCache;
}
TermInfosReader(Directory dir, String seg, FieldInfos fis)
throws CorruptIndexException, IOException {
this(dir, seg, fis, BufferedIndexInput.BUFFER_SIZE);
}
TermInfosReader(Directory dir, String seg, FieldInfos fis, int readBufferSize)
throws CorruptIndexException, IOException {
boolean success = false;
try {
directory = dir;
segment = seg;
fieldInfos = fis;
origEnum = new SegmentTermEnum(directory.openInput(segment + "." + IndexFileNames.TERMS_EXTENSION,
readBufferSize), fieldInfos, false);
size = origEnum.size;
totalIndexInterval = origEnum.indexInterval;
indexEnum = new SegmentTermEnum(directory.openInput(segment + "." + IndexFileNames.TERMS_INDEX_EXTENSION,
readBufferSize), fieldInfos, true);
success = true;
} finally {
// With lock-less commits, it's entirely possible (and
// fine) to hit a FileNotFound exception above. In
// this case, we want to explicitly close any subset
// of things that were opened so that we don't have to
// wait for a GC to do so.
if (!success) {
close();
}
}
}
public int getSkipInterval() {
return origEnum.skipInterval;
}
public int getMaxSkipLevels() {
return origEnum.maxSkipLevels;
}
/**
* <p>Sets the indexDivisor, which subsamples the number
* of indexed terms loaded into memory. This has a
* similar effect as {@link
* IndexWriter#setTermIndexInterval} except that setting
* must be done at indexing time while this setting can be
* set per reader. When set to N, then one in every
* N*termIndexInterval terms in the index is loaded into
* memory. By setting this to a value > 1 you can reduce
* memory usage, at the expense of higher latency when
* loading a TermInfo. The default value is 1.</p>
*
* <b>NOTE:</b> you must call this before the term
* index is loaded. If the index is already loaded,
* an IllegalStateException is thrown.
*
+ @throws IllegalStateException if the term index has
* already been loaded into memory.
*/
public void setIndexDivisor(int indexDivisor) throws IllegalStateException {
if (indexDivisor < 1)
throw new IllegalArgumentException("indexDivisor must be > 0: got " + indexDivisor);
if (indexTerms != null)
throw new IllegalStateException("index terms are already loaded");
this.indexDivisor = indexDivisor;
totalIndexInterval = origEnum.indexInterval * indexDivisor;
}
/** Returns the indexDivisor.
* @see #setIndexDivisor
*/
public int getIndexDivisor() {
return indexDivisor;
}
final void close() throws IOException {
if (origEnum != null)
origEnum.close();
if (indexEnum != null)
indexEnum.close();
threadResources.close();
}
/** Returns the number of term/value pairs in the set. */
final long size() {
return size;
}
private ThreadResources getThreadResources() {
ThreadResources resources = (ThreadResources)threadResources.get();
if (resources == null) {
resources = new ThreadResources();
resources.termEnum = terms();
// Cache does not have to be thread-safe, it is only used by one thread at the same time
resources.termInfoCache = new SimpleLRUCache(DEFAULT_CACHE_SIZE);
threadResources.set(resources);
}
return resources;
}
private synchronized void ensureIndexIsRead() throws IOException {
if (indexTerms != null) // index already read
return; // do nothing
try {
int indexSize = 1+((int)indexEnum.size-1)/indexDivisor; // otherwise read index
indexTerms = new Term[indexSize];
indexInfos = new TermInfo[indexSize];
indexPointers = new long[indexSize];
for (int i = 0; indexEnum.next(); i++) {
indexTerms[i] = indexEnum.term();
indexInfos[i] = indexEnum.termInfo();
indexPointers[i] = indexEnum.indexPointer;
for (int j = 1; j < indexDivisor; j++)
if (!indexEnum.next())
break;
}
} finally {
indexEnum.close();
indexEnum = null;
}
}
/** Returns the offset of the greatest index entry which is less than or equal to term.*/
private final int getIndexOffset(Term term) {
int lo = 0; // binary search indexTerms[]
int hi = indexTerms.length - 1;
while (hi >= lo) {
int mid = (lo + hi) >> 1;
int delta = term.compareTo(indexTerms[mid]);
if (delta < 0)
hi = mid - 1;
else if (delta > 0)
lo = mid + 1;
else
return mid;
}
return hi;
}
private final void seekEnum(SegmentTermEnum enumerator, int indexOffset) throws IOException {
enumerator.seek(indexPointers[indexOffset],
(indexOffset * totalIndexInterval) - 1,
indexTerms[indexOffset], indexInfos[indexOffset]);
}
/** Returns the TermInfo for a Term in the set, or null. */
TermInfo get(Term term) throws IOException {
return get(term, true);
}
/** Returns the TermInfo for a Term in the set, or null. */
private TermInfo get(Term term, boolean useCache) throws IOException {
if (size == 0) return null;
ensureIndexIsRead();
TermInfo ti;
ThreadResources resources = getThreadResources();
Cache cache = null;
if (useCache) {
cache = resources.termInfoCache;
// check the cache first if the term was recently looked up
ti = (TermInfo) cache.get(term);
if (ti != null) {
return ti;
}
}
// optimize sequential access: first try scanning cached enum w/o seeking
SegmentTermEnum enumerator = resources.termEnum;
if (enumerator.term() != null // term is at or past current
&& ((enumerator.prev() != null && term.compareTo(enumerator.prev())> 0)
|| term.compareTo(enumerator.term()) >= 0)) {
int enumOffset = (int)(enumerator.position/totalIndexInterval)+1;
if (indexTerms.length == enumOffset // but before end of block
|| term.compareTo(indexTerms[enumOffset]) < 0) {
// no need to seek
int numScans = enumerator.scanTo(term);
if (enumerator.term() != null && term.compareTo(enumerator.term()) == 0) {
ti = enumerator.termInfo();
if (cache != null && numScans > 1) {
// we only want to put this TermInfo into the cache if
// scanEnum skipped more than one dictionary entry.
// This prevents RangeQueries or WildcardQueries to
// wipe out the cache when they iterate over a large numbers
// of terms in order
cache.put(term, ti);
}
} else {
ti = null;
}
return ti;
}
}
// random-access: must seek
seekEnum(enumerator, getIndexOffset(term));
enumerator.scanTo(term);
if (enumerator.term() != null && term.compareTo(enumerator.term()) == 0) {
ti = enumerator.termInfo();
if (cache != null) {
cache.put(term, ti);
}
} else {
ti = null;
}
return ti;
}
/** Returns the nth term in the set. */
final Term get(int position) throws IOException {
if (size == 0) return null;
SegmentTermEnum enumerator = getThreadResources().termEnum;
if (enumerator != null && enumerator.term() != null &&
position >= enumerator.position &&
position < (enumerator.position + totalIndexInterval))
return scanEnum(enumerator, position); // can avoid seek
seekEnum(enumerator, position/totalIndexInterval); // must seek
return scanEnum(enumerator, position);
}
private final Term scanEnum(SegmentTermEnum enumerator, int position) throws IOException {
while(enumerator.position < position)
if (!enumerator.next())
return null;
return enumerator.term();
}
/** Returns the position of a Term in the set or -1. */
final long getPosition(Term term) throws IOException {
if (size == 0) return -1;
ensureIndexIsRead();
int indexOffset = getIndexOffset(term);
SegmentTermEnum enumerator = getThreadResources().termEnum;
seekEnum(enumerator, indexOffset);
while(term.compareTo(enumerator.term()) > 0 && enumerator.next()) {}
if (term.compareTo(enumerator.term()) == 0)
return enumerator.position;
else
return -1;
}
/** Returns an enumeration of all the Terms and TermInfos in the set. */
public SegmentTermEnum terms() {
return (SegmentTermEnum)origEnum.clone();
}
/** Returns an enumeration of terms starting at or after the named term. */
public SegmentTermEnum terms(Term term) throws IOException {
// don't use the cache in this call because we want to reposition the
// enumeration
get(term, false);
return (SegmentTermEnum)getThreadResources().termEnum.clone();
}
}