package org.apache.lucene.codecs.lucene40;
/*
* 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.codecs.CodecUtil;
import org.apache.lucene.codecs.TermVectorsFormat;
import org.apache.lucene.codecs.TermVectorsReader;
import org.apache.lucene.codecs.TermVectorsWriter;
import org.apache.lucene.index.FieldInfos;
import org.apache.lucene.index.SegmentInfo;
import org.apache.lucene.store.DataOutput; // javadocs
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.IOContext;
/**
* Lucene 4.0 Term Vectors format.
* <p>Term Vector support is an optional on a field by field basis. It consists of
* 3 files.</p>
* <ol>
* <li><a name="tvx" id="tvx"></a>
* <p>The Document Index or .tvx file.</p>
* <p>For each document, this stores the offset into the document data (.tvd) and
* field data (.tvf) files.</p>
* <p>DocumentIndex (.tvx) --> Header,<DocumentPosition,FieldPosition>
* <sup>NumDocs</sup></p>
* <ul>
* <li>Header --> {@link CodecUtil#writeHeader CodecHeader}</li>
* <li>DocumentPosition --> {@link DataOutput#writeLong UInt64} (offset in the .tvd file)</li>
* <li>FieldPosition --> {@link DataOutput#writeLong UInt64} (offset in the .tvf file)</li>
* </ul>
* </li>
* <li><a name="tvd" id="tvd"></a>
* <p>The Document or .tvd file.</p>
* <p>This contains, for each document, the number of fields, a list of the fields
* with term vector info and finally a list of pointers to the field information
* in the .tvf (Term Vector Fields) file.</p>
* <p>The .tvd file is used to map out the fields that have term vectors stored
* and where the field information is in the .tvf file.</p>
* <p>Document (.tvd) --> Header,<NumFields, FieldNums,
* FieldPositions> <sup>NumDocs</sup></p>
* <ul>
* <li>Header --> {@link CodecUtil#writeHeader CodecHeader}</li>
* <li>NumFields --> {@link DataOutput#writeVInt VInt}</li>
* <li>FieldNums --> <FieldNumDelta> <sup>NumFields</sup></li>
* <li>FieldNumDelta --> {@link DataOutput#writeVInt VInt}</li>
* <li>FieldPositions --> <FieldPositionDelta> <sup>NumFields-1</sup></li>
* <li>FieldPositionDelta --> {@link DataOutput#writeVLong VLong}</li>
* </ul>
* </li>
* <li><a name="tvf" id="tvf"></a>
* <p>The Field or .tvf file.</p>
* <p>This file contains, for each field that has a term vector stored, a list of
* the terms, their frequencies and, optionally, position, offset, and payload
* information.</p>
* <p>Field (.tvf) --> Header,<NumTerms, Flags, TermFreqs>
* <sup>NumFields</sup></p>
* <ul>
* <li>Header --> {@link CodecUtil#writeHeader CodecHeader}</li>
* <li>NumTerms --> {@link DataOutput#writeVInt VInt}</li>
* <li>Flags --> {@link DataOutput#writeByte Byte}</li>
* <li>TermFreqs --> <TermText, TermFreq, Positions?, PayloadData?, Offsets?>
* <sup>NumTerms</sup></li>
* <li>TermText --> <PrefixLength, Suffix></li>
* <li>PrefixLength --> {@link DataOutput#writeVInt VInt}</li>
* <li>Suffix --> {@link DataOutput#writeString String}</li>
* <li>TermFreq --> {@link DataOutput#writeVInt VInt}</li>
* <li>Positions --> <PositionDelta PayloadLength?><sup>TermFreq</sup></li>
* <li>PositionDelta --> {@link DataOutput#writeVInt VInt}</li>
* <li>PayloadLength --> {@link DataOutput#writeVInt VInt}</li>
* <li>PayloadData --> {@link DataOutput#writeByte Byte}<sup>NumPayloadBytes</sup></li>
* <li>Offsets --> <{@link DataOutput#writeVInt VInt}, {@link DataOutput#writeVInt VInt}><sup>TermFreq</sup></li>
* </ul>
* <p>Notes:</p>
* <ul>
* <li>Flags byte stores whether this term vector has position, offset, payload.
* information stored.</li>
* <li>Term byte prefixes are shared. The PrefixLength is the number of initial
* bytes from the previous term which must be pre-pended to a term's suffix
* in order to form the term's bytes. Thus, if the previous term's text was "bone"
* and the term is "boy", the PrefixLength is two and the suffix is "y".</li>
* <li>PositionDelta is, if payloads are disabled for the term's field, the
* difference between the position of the current occurrence in the document and
* the previous occurrence (or zero, if this is the first occurrence in this
* document). If payloads are enabled for the term's field, then PositionDelta/2
* is the difference between the current and the previous position. If payloads
* are enabled and PositionDelta is odd, then PayloadLength is stored, indicating
* the length of the payload at the current term position.</li>
* <li>PayloadData is metadata associated with a term position. If
* PayloadLength is stored at the current position, then it indicates the length
* of this payload. If PayloadLength is not stored, then this payload has the same
* length as the payload at the previous position. PayloadData encodes the
* concatenated bytes for all of a terms occurrences.</li>
* <li>Offsets are stored as delta encoded VInts. The first VInt is the
* startOffset, the second is the endOffset.</li>
* </ul>
* </li>
* </ol>
*/
public class Lucene40TermVectorsFormat extends TermVectorsFormat {
/** Sole constructor. */
public Lucene40TermVectorsFormat() {
}
@Override
public TermVectorsReader vectorsReader(Directory directory, SegmentInfo segmentInfo, FieldInfos fieldInfos, IOContext context) throws IOException {
return new Lucene40TermVectorsReader(directory, segmentInfo, fieldInfos, context);
}
@Override
public TermVectorsWriter vectorsWriter(Directory directory, SegmentInfo segmentInfo, IOContext context) throws IOException {
return new Lucene40TermVectorsWriter(directory, segmentInfo.name, context);
}
}