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The source code

package org.apache.lucene.index;

/**
 * Copyright 2004 The Apache Software Foundation
 *
 * 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.
 */

import java.util.Vector;
import java.util.ArrayList;
import java.util.Iterator;
import java.io.IOException;

import org.apache.lucene.store.Directory;
import org.apache.lucene.store.OutputStream;
import org.apache.lucene.store.RAMOutputStream;

/**
 * The SegmentMerger class combines two or more Segments, represented by an IndexReader ({@link #add},
 * into a single Segment.  After adding the appropriate readers, call the merge method to combine the 
 * segments.
 *

* If the compoundFile flag is set, then the segments will be merged into a compound file. * * * @see #merge * @see #add */ final class SegmentMerger { private boolean useCompoundFile; private Directory directory; private String segment; private Vector readers = new Vector(); private FieldInfos fieldInfos; // File extensions of old-style index files private static final String COMPOUND_EXTENSIONS[] = new String[] { "fnm", "frq", "prx", "fdx", "fdt", "tii", "tis" }; private static final String VECTOR_EXTENSIONS[] = new String[] { "tvx", "tvd", "tvf" }; /** * * @param dir The Directory to merge the other segments into * @param name The name of the new segment * @param compoundFile true if the new segment should use a compoundFile */ SegmentMerger(Directory dir, String name, boolean compoundFile) { directory = dir; segment = name; useCompoundFile = compoundFile; } /** * Add an IndexReader to the collection of readers that are to be merged * @param reader */ final void add(IndexReader reader) { readers.addElement(reader); } /** * * @param i The index of the reader to return * @return The ith reader to be merged */ final IndexReader segmentReader(int i) { return (IndexReader) readers.elementAt(i); } /** * Merges the readers specified by the {@link #add} method into the directory passed to the constructor * @return The number of documents that were merged * @throws IOException */ final int merge() throws IOException { int value; value = mergeFields(); mergeTerms(); mergeNorms(); if (fieldInfos.hasVectors()) mergeVectors(); if (useCompoundFile) createCompoundFile(); return value; } /** * close all IndexReaders that have been added. * Should not be called before merge(). * @throws IOException */ final void closeReaders() throws IOException { for (int i = 0; i < readers.size(); i++) { // close readers IndexReader reader = (IndexReader) readers.elementAt(i); reader.close(); } } private final void createCompoundFile() throws IOException { CompoundFileWriter cfsWriter = new CompoundFileWriter(directory, segment + ".cfs"); ArrayList files = new ArrayList(COMPOUND_EXTENSIONS.length + fieldInfos.size()); // Basic files for (int i = 0; i < COMPOUND_EXTENSIONS.length; i++) { files.add(segment + "." + COMPOUND_EXTENSIONS[i]); } // Field norm files for (int i = 0; i < fieldInfos.size(); i++) { FieldInfo fi = fieldInfos.fieldInfo(i); if (fi.isIndexed) { files.add(segment + ".f" + i); } } // Vector files if (fieldInfos.hasVectors()) { for (int i = 0; i < VECTOR_EXTENSIONS.length; i++) { files.add(segment + "." + VECTOR_EXTENSIONS[i]); } } // Now merge all added files Iterator it = files.iterator(); while (it.hasNext()) { cfsWriter.addFile((String) it.next()); } // Perform the merge cfsWriter.close(); // Now delete the source files it = files.iterator(); while (it.hasNext()) { directory.deleteFile((String) it.next()); } } /** * * @return The number of documents in all of the readers * @throws IOException */ private final int mergeFields() throws IOException { fieldInfos = new FieldInfos(); // merge field names int docCount = 0; for (int i = 0; i < readers.size(); i++) { IndexReader reader = (IndexReader) readers.elementAt(i); fieldInfos.addIndexed(reader.getIndexedFieldNames(true), true); fieldInfos.addIndexed(reader.getIndexedFieldNames(false), false); fieldInfos.add(reader.getFieldNames(false), false); } fieldInfos.write(directory, segment + ".fnm"); FieldsWriter fieldsWriter = // merge field values new FieldsWriter(directory, segment, fieldInfos); try { for (int i = 0; i < readers.size(); i++) { IndexReader reader = (IndexReader) readers.elementAt(i); int maxDoc = reader.maxDoc(); for (int j = 0; j < maxDoc; j++) if (!reader.isDeleted(j)) { // skip deleted docs fieldsWriter.addDocument(reader.document(j)); docCount++; } } } finally { fieldsWriter.close(); } return docCount; } /** * Merge the TermVectors from each of the segments into the new one. * @throws IOException */ private final void mergeVectors() throws IOException { TermVectorsWriter termVectorsWriter = new TermVectorsWriter(directory, segment, fieldInfos); try { for (int r = 0; r < readers.size(); r++) { IndexReader reader = (IndexReader) readers.elementAt(r); int maxDoc = reader.maxDoc(); for (int docNum = 0; docNum < maxDoc; docNum++) { // skip deleted docs if (reader.isDeleted(docNum)) { continue; } termVectorsWriter.openDocument(); // get all term vectors TermFreqVector[] sourceTermVector = reader.getTermFreqVectors(docNum); if (sourceTermVector != null) { for (int f = 0; f < sourceTermVector.length; f++) { // translate field numbers TermFreqVector termVector = sourceTermVector[f]; termVectorsWriter.openField(termVector.getField()); String [] terms = termVector.getTerms(); int [] freqs = termVector.getTermFrequencies(); for (int t = 0; t < terms.length; t++) { termVectorsWriter.addTerm(terms[t], freqs[t]); } } termVectorsWriter.closeDocument(); } } } } finally { termVectorsWriter.close(); } } private OutputStream freqOutput = null; private OutputStream proxOutput = null; private TermInfosWriter termInfosWriter = null; private int skipInterval; private SegmentMergeQueue queue = null; private final void mergeTerms() throws IOException { try { freqOutput = directory.createFile(segment + ".frq"); proxOutput = directory.createFile(segment + ".prx"); termInfosWriter = new TermInfosWriter(directory, segment, fieldInfos); skipInterval = termInfosWriter.skipInterval; queue = new SegmentMergeQueue(readers.size()); mergeTermInfos(); } finally { if (freqOutput != null) freqOutput.close(); if (proxOutput != null) proxOutput.close(); if (termInfosWriter != null) termInfosWriter.close(); if (queue != null) queue.close(); } } private final void mergeTermInfos() throws IOException { int base = 0; for (int i = 0; i < readers.size(); i++) { IndexReader reader = (IndexReader) readers.elementAt(i); TermEnum termEnum = reader.terms(); SegmentMergeInfo smi = new SegmentMergeInfo(base, termEnum, reader); base += reader.numDocs(); if (smi.next()) queue.put(smi); // initialize queue else smi.close(); } SegmentMergeInfo[] match = new SegmentMergeInfo[readers.size()]; while (queue.size() > 0) { int matchSize = 0; // pop matching terms match[matchSize++] = (SegmentMergeInfo) queue.pop(); Term term = match[0].term; SegmentMergeInfo top = (SegmentMergeInfo) queue.top(); while (top != null && term.compareTo(top.term) == 0) { match[matchSize++] = (SegmentMergeInfo) queue.pop(); top = (SegmentMergeInfo) queue.top(); } mergeTermInfo(match, matchSize); // add new TermInfo while (matchSize > 0) { SegmentMergeInfo smi = match[--matchSize]; if (smi.next()) queue.put(smi); // restore queue else smi.close(); // done with a segment } } } private final TermInfo termInfo = new TermInfo(); // minimize consing /** Merge one term found in one or more segments. The array smis * contains segments that are positioned at the same term. N * is the number of cells in the array actually occupied. * * @param smis array of segments * @param n number of cells in the array actually occupied */ private final void mergeTermInfo(SegmentMergeInfo[] smis, int n) throws IOException { long freqPointer = freqOutput.getFilePointer(); long proxPointer = proxOutput.getFilePointer(); int df = appendPostings(smis, n); // append posting data long skipPointer = writeSkip(); if (df > 0) { // add an entry to the dictionary with pointers to prox and freq files termInfo.set(df, freqPointer, proxPointer, (int) (skipPointer - freqPointer)); termInfosWriter.add(smis[0].term, termInfo); } } /** Process postings from multiple segments all positioned on the * same term. Writes out merged entries into freqOutput and * the proxOutput streams. * * @param smis array of segments * @param n number of cells in the array actually occupied * @return number of documents across all segments where this term was found */ private final int appendPostings(SegmentMergeInfo[] smis, int n) throws IOException { int lastDoc = 0; int df = 0; // number of docs w/ term resetSkip(); for (int i = 0; i < n; i++) { SegmentMergeInfo smi = smis[i]; TermPositions postings = smi.postings; int base = smi.base; int[] docMap = smi.docMap; postings.seek(smi.termEnum); while (postings.next()) { int doc = postings.doc(); if (docMap != null) doc = docMap[doc]; // map around deletions doc += base; // convert to merged space if (doc < lastDoc) throw new IllegalStateException("docs out of order"); df++; if ((df % skipInterval) == 0) { bufferSkip(lastDoc); } int docCode = (doc - lastDoc) << 1; // use low bit to flag freq=1 lastDoc = doc; int freq = postings.freq(); if (freq == 1) { freqOutput.writeVInt(docCode | 1); // write doc & freq=1 } else { freqOutput.writeVInt(docCode); // write doc freqOutput.writeVInt(freq); // write frequency in doc } int lastPosition = 0; // write position deltas for (int j = 0; j < freq; j++) { int position = postings.nextPosition(); proxOutput.writeVInt(position - lastPosition); lastPosition = position; } } } return df; } private RAMOutputStream skipBuffer = new RAMOutputStream(); private int lastSkipDoc; private long lastSkipFreqPointer; private long lastSkipProxPointer; private void resetSkip() throws IOException { skipBuffer.reset(); lastSkipDoc = 0; lastSkipFreqPointer = freqOutput.getFilePointer(); lastSkipProxPointer = proxOutput.getFilePointer(); } private void bufferSkip(int doc) throws IOException { long freqPointer = freqOutput.getFilePointer(); long proxPointer = proxOutput.getFilePointer(); skipBuffer.writeVInt(doc - lastSkipDoc); skipBuffer.writeVInt((int) (freqPointer - lastSkipFreqPointer)); skipBuffer.writeVInt((int) (proxPointer - lastSkipProxPointer)); lastSkipDoc = doc; lastSkipFreqPointer = freqPointer; lastSkipProxPointer = proxPointer; } private long writeSkip() throws IOException { long skipPointer = freqOutput.getFilePointer(); skipBuffer.writeTo(freqOutput); return skipPointer; } private void mergeNorms() throws IOException { for (int i = 0; i < fieldInfos.size(); i++) { FieldInfo fi = fieldInfos.fieldInfo(i); if (fi.isIndexed) { OutputStream output = directory.createFile(segment + ".f" + i); try { for (int j = 0; j < readers.size(); j++) { IndexReader reader = (IndexReader) readers.elementAt(j); byte[] input = reader.norms(fi.name); int maxDoc = reader.maxDoc(); for (int k = 0; k < maxDoc; k++) { byte norm = input != null ? input[k] : (byte) 0; if (!reader.isDeleted(k)) { output.writeByte(norm); } } } } finally { output.close(); } } } } }

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