| /* |
| * 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.backward_codecs.lucene50; |
| |
| import org.apache.lucene.backward_codecs.lucene50.compressing.Lucene50CompressingTermVectorsFormat; |
| import org.apache.lucene.backward_codecs.lucene87.Lucene87StoredFieldsFormat; |
| import org.apache.lucene.codecs.CodecUtil; |
| import org.apache.lucene.codecs.TermVectorsFormat; |
| 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 id="vector_data"></a> |
| * <p>A vector data file (extension <code>.tvd</code>). 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>Here is a more detailed description of the field data file format: |
| * <ul> |
| * <li>VectorData (.tvd) --> <Header>, PackedIntsVersion, ChunkSize, |
| * <Chunk><sup>ChunkCount</sup>, ChunkCount, DirtyChunkCount, Footer |
| * <li>Header --> {@link CodecUtil#writeIndexHeader IndexHeader} |
| * <li>PackedIntsVersion --> {@link PackedInts#VERSION_CURRENT} as a {@link |
| * DataOutput#writeVInt VInt} |
| * <li>ChunkSize is the number of bytes of terms to accumulate before flushing, as a {@link |
| * DataOutput#writeVInt VInt} |
| * <li>ChunkCount is not known in advance and is the number of chunks necessary to store all |
| * document of the segment |
| * <li>Chunk --> DocBase, ChunkDocs, < NumFields >, < FieldNums >, < |
| * FieldNumOffs >, < Flags >, < NumTerms >, < TermLengths >, < |
| * TermFreqs >, < Positions >, < StartOffsets >, < Lengths >, < |
| * PayloadLengths >, < TermAndPayloads > |
| * <li>DocBase is the ID of the first doc of the chunk as a {@link DataOutput#writeVInt |
| * VInt} |
| * <li>ChunkDocs is the number of documents in the chunk |
| * <li>NumFields --> DocNumFields<sup>ChunkDocs</sup> |
| * <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>FieldNums --> FieldNumDelta<sup>TotalDistincFields</sup>, a delta-encoded list of |
| * the sorted unique field numbers present in the chunk |
| * <li>FieldNumOffs --> FieldNumOff<sup>TotalFields</sup>, as a {@link PackedInts} array |
| * <li>FieldNumOff is the offset of the field number in FieldNums |
| * <li>TotalFields is the total number of fields (sum of the values of NumFields) |
| * <li>Flags --> Bit < FieldFlags > |
| * <li>Bit is a single bit which when true means that fields have the same options for every |
| * document in the chunk |
| * <li>FieldFlags --> if Bit==1: Flag<sup>TotalDistinctFields</sup> else |
| * Flag<sup>TotalFields</sup> |
| * <li>Flag: a 3-bits int where: |
| * <ul> |
| * <li>the first bit means that the field has positions |
| * <li>the second bit means that the field has offsets |
| * <li>the third bit means that the field has payloads |
| * </ul> |
| * <li>NumTerms --> FieldNumTerms<sup>TotalFields</sup> |
| * <li>FieldNumTerms: the number of terms for each field, using {@link BlockPackedWriter |
| * blocks of 64 packed ints} |
| * <li>TermLengths --> PrefixLength<sup>TotalTerms</sup> |
| * SuffixLength<sup>TotalTerms</sup> |
| * <li>TotalTerms: total number of terms (sum of NumTerms) |
| * <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>SuffixLength: length of the term minus PrefixLength for every term using {@link |
| * BlockPackedWriter blocks of 64 packed ints} |
| * <li>TermFreqs --> TermFreqMinus1<sup>TotalTerms</sup> |
| * <li>TermFreqMinus1: (frequency - 1) for each term using {@link BlockPackedWriter blocks |
| * of 64 packed ints} |
| * <li>Positions --> PositionDelta<sup>TotalPositions</sup> |
| * <li>TotalPositions is the sum of frequencies of terms of all fields that have positions |
| * <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>StartOffsets --> (AvgCharsPerTerm<sup>TotalDistinctFields</sup>) |
| * StartOffsetDelta<sup>TotalOffsets</sup> |
| * <li>TotalOffsets is the sum of frequencies of terms of all fields that have offsets |
| * <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>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>Lengths --> LengthMinusTermLength<sup>TotalOffsets</sup> |
| * <li>LengthMinusTermLength: (endOffset - startOffset - termLength) using {@link |
| * BlockPackedWriter blocks of 64 packed ints} |
| * <li>PayloadLengths --> PayloadLength<sup>TotalPayloads</sup> |
| * <li>TotalPayloads is the sum of frequencies of terms of all fields that have payloads |
| * <li>PayloadLength is the payload length encoded using {@link BlockPackedWriter blocks of |
| * 64 packed ints} |
| * <li>TermAndPayloads --> LZ4-compressed representation of < FieldTermsAndPayLoads |
| * ><sup>TotalFields</sup> |
| * <li>FieldTermsAndPayLoads --> Terms (Payloads) |
| * <li>Terms: term bytes |
| * <li>Payloads: payload bytes (if the field has payloads) |
| * <li>ChunkCount --> the number of chunks in this file |
| * <li>DirtyChunkCount --> the number of prematurely flushed chunks in this file |
| * <li>Footer --> {@link CodecUtil#writeFooter CodecFooter} |
| * </ul> |
| * <li><a id="vector_index"></a> |
| * <p>An index file (extension <code>.tvx</code>). |
| * <ul> |
| * <li>VectorIndex (.tvx) --> <Header>, <ChunkIndex>, Footer |
| * <li>Header --> {@link CodecUtil#writeIndexHeader IndexHeader} |
| * <li>ChunkIndex: See FieldsIndexWriter |
| * <li>Footer --> {@link CodecUtil#writeFooter CodecFooter} |
| * </ul> |
| * </ol> |
| * |
| * @lucene.experimental |
| */ |
| public final class Lucene50TermVectorsFormat extends Lucene50CompressingTermVectorsFormat { |
| |
| /** Sole constructor. */ |
| public Lucene50TermVectorsFormat() { |
| super("Lucene50TermVectorsData", "", CompressionMode.FAST, 1 << 12, 10); |
| } |
| } |
