| /* |
| * 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.codecs.lucene50; |
| |
| |
| import org.apache.lucene.codecs.CodecUtil; |
| import org.apache.lucene.codecs.TermVectorsFormat; |
| import org.apache.lucene.codecs.compressing.FieldsIndexWriter; |
| import org.apache.lucene.codecs.lucene87.Lucene87StoredFieldsFormat; |
| import org.apache.lucene.codecs.compressing.CompressingTermVectorsFormat; |
| import org.apache.lucene.codecs.compressing.CompressionMode; |
| import org.apache.lucene.store.DataOutput; |
| import org.apache.lucene.util.packed.BlockPackedWriter; |
| import org.apache.lucene.util.packed.PackedInts; |
| |
| /** |
| * Lucene 5.0 {@link TermVectorsFormat term vectors format}. |
| * <p> |
| * Very similarly to {@link Lucene87StoredFieldsFormat}, this format is based |
| * on compressed chunks of data, with document-level granularity so that a |
| * document can never span across distinct chunks. Moreover, data is made as |
| * compact as possible:<ul> |
| * <li>textual data is compressed using the very light, |
| * <a href="http://code.google.com/p/lz4/">LZ4</a> compression algorithm, |
| * <li>binary data is written using fixed-size blocks of |
| * {@link PackedInts packed ints}. |
| * </ul> |
| * <p> |
| * Term vectors are stored using two files<ul> |
| * <li>a data file where terms, frequencies, positions, offsets and payloads |
| * are stored, |
| * <li>an index file, loaded into memory, used to locate specific documents in |
| * the data file. |
| * </ul> |
| * Looking up term vectors for any document requires at most 1 disk seek. |
| * <p><b>File formats</b> |
| * <ol> |
| * <li><a name="vector_data"></a> |
| * <p>A vector data file (extension <tt>.tvd</tt>). This file stores terms, |
| * frequencies, positions, offsets and payloads for every document. Upon writing |
| * a new segment, it accumulates data into memory until the buffer used to store |
| * terms and payloads grows beyond 4KB. Then it flushes all metadata, terms |
| * and positions to disk using <a href="http://code.google.com/p/lz4/">LZ4</a> |
| * compression for terms and payloads and |
| * {@link BlockPackedWriter blocks of packed ints} for positions.</p> |
| * <p>Here is a more detailed description of the field data file format:</p> |
| * <ul> |
| * <li>VectorData (.tvd) --> <Header>, PackedIntsVersion, ChunkSize, <Chunk><sup>ChunkCount</sup>, ChunkCount, DirtyChunkCount, Footer</li> |
| * <li>Header --> {@link CodecUtil#writeIndexHeader IndexHeader}</li> |
| * <li>PackedIntsVersion --> {@link PackedInts#VERSION_CURRENT} as a {@link DataOutput#writeVInt VInt}</li> |
| * <li>ChunkSize is the number of bytes of terms to accumulate before flushing, as a {@link DataOutput#writeVInt VInt}</li> |
| * <li>ChunkCount is not known in advance and is the number of chunks necessary to store all document of the segment</li> |
| * <li>Chunk --> DocBase, ChunkDocs, < NumFields >, < FieldNums >, < FieldNumOffs >, < Flags >, |
| * < NumTerms >, < TermLengths >, < TermFreqs >, < Positions >, < StartOffsets >, < Lengths >, |
| * < PayloadLengths >, < TermAndPayloads ></li> |
| * <li>DocBase is the ID of the first doc of the chunk as a {@link DataOutput#writeVInt VInt}</li> |
| * <li>ChunkDocs is the number of documents in the chunk</li> |
| * <li>NumFields --> DocNumFields<sup>ChunkDocs</sup></li> |
| * <li>DocNumFields is the number of fields for each doc, written as a {@link DataOutput#writeVInt VInt} if ChunkDocs==1 and as a {@link PackedInts} array otherwise</li> |
| * <li>FieldNums --> FieldNumDelta<sup>TotalDistincFields</sup>, a delta-encoded list of the sorted unique field numbers present in the chunk</li> |
| * <li>FieldNumOffs --> FieldNumOff<sup>TotalFields</sup>, as a {@link PackedInts} array</li> |
| * <li>FieldNumOff is the offset of the field number in FieldNums</li> |
| * <li>TotalFields is the total number of fields (sum of the values of NumFields)</li> |
| * <li>Flags --> Bit < FieldFlags ></li> |
| * <li>Bit is a single bit which when true means that fields have the same options for every document in the chunk</li> |
| * <li>FieldFlags --> if Bit==1: Flag<sup>TotalDistinctFields</sup> else Flag<sup>TotalFields</sup></li> |
| * <li>Flag: a 3-bits int where:<ul> |
| * <li>the first bit means that the field has positions</li> |
| * <li>the second bit means that the field has offsets</li> |
| * <li>the third bit means that the field has payloads</li> |
| * </ul></li> |
| * <li>NumTerms --> FieldNumTerms<sup>TotalFields</sup></li> |
| * <li>FieldNumTerms: the number of terms for each field, using {@link BlockPackedWriter blocks of 64 packed ints}</li> |
| * <li>TermLengths --> PrefixLength<sup>TotalTerms</sup> SuffixLength<sup>TotalTerms</sup></li> |
| * <li>TotalTerms: total number of terms (sum of NumTerms)</li> |
| * <li>PrefixLength: 0 for the first term of a field, the common prefix with the previous term otherwise using {@link BlockPackedWriter blocks of 64 packed ints}</li> |
| * <li>SuffixLength: length of the term minus PrefixLength for every term using {@link BlockPackedWriter blocks of 64 packed ints}</li> |
| * <li>TermFreqs --> TermFreqMinus1<sup>TotalTerms</sup></li> |
| * <li>TermFreqMinus1: (frequency - 1) for each term using {@link BlockPackedWriter blocks of 64 packed ints}</li> |
| * <li>Positions --> PositionDelta<sup>TotalPositions</sup></li> |
| * <li>TotalPositions is the sum of frequencies of terms of all fields that have positions</li> |
| * <li>PositionDelta: the absolute position for the first position of a term, and the difference with the previous positions for following positions using {@link BlockPackedWriter blocks of 64 packed ints}</li> |
| * <li>StartOffsets --> (AvgCharsPerTerm<sup>TotalDistinctFields</sup>) StartOffsetDelta<sup>TotalOffsets</sup></li> |
| * <li>TotalOffsets is the sum of frequencies of terms of all fields that have offsets</li> |
| * <li>AvgCharsPerTerm: average number of chars per term, encoded as a float on 4 bytes. They are not present if no field has both positions and offsets enabled.</li> |
| * <li>StartOffsetDelta: (startOffset - previousStartOffset - AvgCharsPerTerm * PositionDelta). previousStartOffset is 0 for the first offset and AvgCharsPerTerm is 0 if the field has no positions using {@link BlockPackedWriter blocks of 64 packed ints}</li> |
| * <li>Lengths --> LengthMinusTermLength<sup>TotalOffsets</sup></li> |
| * <li>LengthMinusTermLength: (endOffset - startOffset - termLength) using {@link BlockPackedWriter blocks of 64 packed ints}</li> |
| * <li>PayloadLengths --> PayloadLength<sup>TotalPayloads</sup></li> |
| * <li>TotalPayloads is the sum of frequencies of terms of all fields that have payloads</li> |
| * <li>PayloadLength is the payload length encoded using {@link BlockPackedWriter blocks of 64 packed ints}</li> |
| * <li>TermAndPayloads --> LZ4-compressed representation of < FieldTermsAndPayLoads ><sup>TotalFields</sup></li> |
| * <li>FieldTermsAndPayLoads --> Terms (Payloads)</li> |
| * <li>Terms: term bytes</li> |
| * <li>Payloads: payload bytes (if the field has payloads)</li> |
| * <li>ChunkCount --> the number of chunks in this file</li> |
| * <li>DirtyChunkCount --> the number of prematurely flushed chunks in this file</li> |
| * <li>Footer --> {@link CodecUtil#writeFooter CodecFooter}</li> |
| * </ul> |
| * </li> |
| * <li><a name="vector_index"></a> |
| * <p>An index file (extension <tt>.tvx</tt>). |
| * <ul> |
| * <li>VectorIndex (.tvx) --> <Header>, <ChunkIndex>, Footer</li> |
| * <li>Header --> {@link CodecUtil#writeIndexHeader IndexHeader}</li> |
| * <li>ChunkIndex: See {@link FieldsIndexWriter}</li> |
| * <li>Footer --> {@link CodecUtil#writeFooter CodecFooter}</li> |
| * </ul> |
| * </li> |
| * </ol> |
| * @lucene.experimental |
| */ |
| public final class Lucene50TermVectorsFormat extends CompressingTermVectorsFormat { |
| |
| /** Sole constructor. */ |
| public Lucene50TermVectorsFormat() { |
| super("Lucene50TermVectorsData", "", CompressionMode.FAST, 1 << 12, 128, 10); |
| } |
| |
| } |