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svn commit: r1621770 [2/2] - in /lucene/dev/branches/lucene5858/lucene:
backward-codecs/src/java/
backward-codecs/src/java/org/apache/lucene/codecs/lucene40/
backward-codecs/src/java/org/apache/lucene/codecs/lucene41/
backward-codecs/src/java/org/apach...
Modified: lucene/dev/branches/lucene5858/lucene/core/src/java/org/apache/lucene/codecs/lucene46/package.html
URL: http://svn.apache.org/viewvc/lucene/dev/branches/lucene5858/lucene/core/src/java/org/apache/lucene/codecs/lucene46/package.html?rev=1621770&r1=1621769&r2=1621770&view=diff
==============================================================================
--- lucene/dev/branches/lucene5858/lucene/core/src/java/org/apache/lucene/codecs/lucene46/package.html (original)
+++ lucene/dev/branches/lucene5858/lucene/core/src/java/org/apache/lucene/codecs/lucene46/package.html Mon Sep 1 13:31:12 2014
@@ -21,381 +21,5 @@
</head>
<body>
Lucene 4.6 file format.
-
-<h1>Apache Lucene - Index File Formats</h1>
-<div>
-<ul>
-<li><a href="#Introduction">Introduction</a></li>
-<li><a href="#Definitions">Definitions</a>
- <ul>
- <li><a href="#Inverted_Indexing">Inverted Indexing</a></li>
- <li><a href="#Types_of_Fields">Types of Fields</a></li>
- <li><a href="#Segments">Segments</a></li>
- <li><a href="#Document_Numbers">Document Numbers</a></li>
- </ul>
-</li>
-<li><a href="#Overview">Index Structure Overview</a></li>
-<li><a href="#File_Naming">File Naming</a></li>
-<li><a href="#file-names">Summary of File Extensions</a></li>
- <ul>
- <li><a href="#Lock_File">Lock File</a></li>
- <li><a href="#History">History</a></li>
- <li><a href="#Limitations">Limitations</a></li>
- </ul>
-</ul>
-</div>
-<a name="Introduction"></a>
-<h2>Introduction</h2>
-<div>
-<p>This document defines the index file formats used in this version of Lucene.
-If you are using a different version of Lucene, please consult the copy of
-<code>docs/</code> that was distributed with
-the version you are using.</p>
-<p>Apache Lucene is written in Java, but several efforts are underway to write
-<a href="http://wiki.apache.org/lucene-java/LuceneImplementations">versions of
-Lucene in other programming languages</a>. If these versions are to remain
-compatible with Apache Lucene, then a language-independent definition of the
-Lucene index format is required. This document thus attempts to provide a
-complete and independent definition of the Apache Lucene file formats.</p>
-<p>As Lucene evolves, this document should evolve. Versions of Lucene in
-different programming languages should endeavor to agree on file formats, and
-generate new versions of this document.</p>
-</div>
-<a name="Definitions" id="Definitions"></a>
-<h2>Definitions</h2>
-<div>
-<p>The fundamental concepts in Lucene are index, document, field and term.</p>
-<p>An index contains a sequence of documents.</p>
-<ul>
-<li>A document is a sequence of fields.</li>
-<li>A field is a named sequence of terms.</li>
-<li>A term is a sequence of bytes.</li>
-</ul>
-<p>The same sequence of bytes in two different fields is considered a different
-term. Thus terms are represented as a pair: the string naming the field, and the
-bytes within the field.</p>
-<a name="Inverted_Indexing"></a>
-<h3>Inverted Indexing</h3>
-<p>The index stores statistics about terms in order to make term-based search
-more efficient. Lucene's index falls into the family of indexes known as an
-<i>inverted index.</i> This is because it can list, for a term, the documents
-that contain it. This is the inverse of the natural relationship, in which
-documents list terms.</p>
-<a name="Types_of_Fields"></a>
-<h3>Types of Fields</h3>
-<p>In Lucene, fields may be <i>stored</i>, in which case their text is stored
-in the index literally, in a non-inverted manner. Fields that are inverted are
-called <i>indexed</i>. A field may be both stored and indexed.</p>
-<p>The text of a field may be <i>tokenized</i> into terms to be indexed, or the
-text of a field may be used literally as a term to be indexed. Most fields are
-tokenized, but sometimes it is useful for certain identifier fields to be
-indexed literally.</p>
-<p>See the {@link org.apache.lucene.document.Field Field}
-java docs for more information on Fields.</p>
-<a name="Segments" id="Segments"></a>
-<h3>Segments</h3>
-<p>Lucene indexes may be composed of multiple sub-indexes, or <i>segments</i>.
-Each segment is a fully independent index, which could be searched separately.
-Indexes evolve by:</p>
-<ol>
-<li>Creating new segments for newly added documents.</li>
-<li>Merging existing segments.</li>
-</ol>
-<p>Searches may involve multiple segments and/or multiple indexes, each index
-potentially composed of a set of segments.</p>
-<a name="Document_Numbers"></a>
-<h3>Document Numbers</h3>
-<p>Internally, Lucene refers to documents by an integer <i>document number</i>.
-The first document added to an index is numbered zero, and each subsequent
-document added gets a number one greater than the previous.</p>
-<p>Note that a document's number may change, so caution should be taken when
-storing these numbers outside of Lucene. In particular, numbers may change in
-the following situations:</p>
-<ul>
-<li>
-<p>The numbers stored in each segment are unique only within the segment, and
-must be converted before they can be used in a larger context. The standard
-technique is to allocate each segment a range of values, based on the range of
-numbers used in that segment. To convert a document number from a segment to an
-external value, the segment's <i>base</i> document number is added. To convert
-an external value back to a segment-specific value, the segment is identified
-by the range that the external value is in, and the segment's base value is
-subtracted. For example two five document segments might be combined, so that
-the first segment has a base value of zero, and the second of five. Document
-three from the second segment would have an external value of eight.</p>
-</li>
-<li>
-<p>When documents are deleted, gaps are created in the numbering. These are
-eventually removed as the index evolves through merging. Deleted documents are
-dropped when segments are merged. A freshly-merged segment thus has no gaps in
-its numbering.</p>
-</li>
-</ul>
-</div>
-<a name="Overview" id="Overview"></a>
-<h2>Index Structure Overview</h2>
-<div>
-<p>Each segment index maintains the following:</p>
-<ul>
-<li>
-{@link org.apache.lucene.codecs.lucene46.Lucene46SegmentInfoFormat Segment info}.
- This contains metadata about a segment, such as the number of documents,
- what files it uses,
-</li>
-<li>
-{@link org.apache.lucene.codecs.lucene46.Lucene46FieldInfosFormat Field names}.
- This contains the set of field names used in the index.
-</li>
-<li>
-{@link org.apache.lucene.codecs.lucene41.Lucene41StoredFieldsFormat Stored Field values}.
-This contains, for each document, a list of attribute-value pairs, where the attributes
-are field names. These are used to store auxiliary information about the document, such as
-its title, url, or an identifier to access a database. The set of stored fields are what is
-returned for each hit when searching. This is keyed by document number.
-</li>
-<li>
-{@link org.apache.lucene.codecs.lucene41.Lucene41PostingsFormat Term dictionary}.
-A dictionary containing all of the terms used in all of the
-indexed fields of all of the documents. The dictionary also contains the number
-of documents which contain the term, and pointers to the term's frequency and
-proximity data.
-</li>
-<li>
-{@link org.apache.lucene.codecs.lucene41.Lucene41PostingsFormat Term Frequency data}.
-For each term in the dictionary, the numbers of all the
-documents that contain that term, and the frequency of the term in that
-document, unless frequencies are omitted (IndexOptions.DOCS_ONLY)
-</li>
-<li>
-{@link org.apache.lucene.codecs.lucene41.Lucene41PostingsFormat Term Proximity data}.
-For each term in the dictionary, the positions that the
-term occurs in each document. Note that this will not exist if all fields in
-all documents omit position data.
-</li>
-<li>
-{@link org.apache.lucene.codecs.lucene42.Lucene42NormsFormat Normalization factors}.
-For each field in each document, a value is stored
-that is multiplied into the score for hits on that field.
-</li>
-<li>
-{@link org.apache.lucene.codecs.lucene42.Lucene42TermVectorsFormat Term Vectors}.
-For each field in each document, the term vector (sometimes
-called document vector) may be stored. A term vector consists of term text and
-term frequency. To add Term Vectors to your index see the
-{@link org.apache.lucene.document.Field Field} constructors
-</li>
-<li>
-{@link org.apache.lucene.codecs.lucene42.Lucene42DocValuesFormat Per-document values}.
-Like stored values, these are also keyed by document
-number, but are generally intended to be loaded into main memory for fast
-access. Whereas stored values are generally intended for summary results from
-searches, per-document values are useful for things like scoring factors.
-</li>
-<li>
-{@link org.apache.lucene.codecs.lucene40.Lucene40LiveDocsFormat Deleted documents}.
-An optional file indicating which documents are deleted.
-</li>
-</ul>
-<p>Details on each of these are provided in their linked pages.</p>
-</div>
-<a name="File_Naming"></a>
-<h2>File Naming</h2>
-<div>
-<p>All files belonging to a segment have the same name with varying extensions.
-The extensions correspond to the different file formats described below. When
-using the Compound File format (default in 1.4 and greater) these files (except
-for the Segment info file, the Lock file, and Deleted documents file) are collapsed
-into a single .cfs file (see below for details)</p>
-<p>Typically, all segments in an index are stored in a single directory,
-although this is not required.</p>
-<p>As of version 2.1 (lock-less commits), file names are never re-used (there
-is one exception, "segments.gen", see below). That is, when any file is saved
-to the Directory it is given a never before used filename. This is achieved
-using a simple generations approach. For example, the first segments file is
-segments_1, then segments_2, etc. The generation is a sequential long integer
-represented in alpha-numeric (base 36) form.</p>
-</div>
-<a name="file-names" id="file-names"></a>
-<h2>Summary of File Extensions</h2>
-<div>
-<p>The following table summarizes the names and extensions of the files in
-Lucene:</p>
-<table cellspacing="1" cellpadding="4">
-<tr>
-<th>Name</th>
-<th>Extension</th>
-<th>Brief Description</th>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.index.SegmentInfos Segments File}</td>
-<td>segments.gen, segments_N</td>
-<td>Stores information about a commit point</td>
-</tr>
-<tr>
-<td><a href="#Lock_File">Lock File</a></td>
-<td>write.lock</td>
-<td>The Write lock prevents multiple IndexWriters from writing to the same
-file.</td>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.codecs.lucene40.Lucene40SegmentInfoFormat Segment Info}</td>
-<td>.si</td>
-<td>Stores metadata about a segment</td>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.store.CompoundFileDirectory Compound File}</td>
-<td>.cfs, .cfe</td>
-<td>An optional "virtual" file consisting of all the other index files for
-systems that frequently run out of file handles.</td>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.codecs.lucene46.Lucene46FieldInfosFormat Fields}</td>
-<td>.fnm</td>
-<td>Stores information about the fields</td>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.codecs.lucene41.Lucene41StoredFieldsFormat Field Index}</td>
-<td>.fdx</td>
-<td>Contains pointers to field data</td>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.codecs.lucene41.Lucene41StoredFieldsFormat Field Data}</td>
-<td>.fdt</td>
-<td>The stored fields for documents</td>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.codecs.lucene41.Lucene41PostingsFormat Term Dictionary}</td>
-<td>.tim</td>
-<td>The term dictionary, stores term info</td>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.codecs.lucene41.Lucene41PostingsFormat Term Index}</td>
-<td>.tip</td>
-<td>The index into the Term Dictionary</td>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.codecs.lucene41.Lucene41PostingsFormat Frequencies}</td>
-<td>.doc</td>
-<td>Contains the list of docs which contain each term along with frequency</td>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.codecs.lucene41.Lucene41PostingsFormat Positions}</td>
-<td>.pos</td>
-<td>Stores position information about where a term occurs in the index</td>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.codecs.lucene41.Lucene41PostingsFormat Payloads}</td>
-<td>.pay</td>
-<td>Stores additional per-position metadata information such as character offsets and user payloads</td>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.codecs.lucene42.Lucene42NormsFormat Norms}</td>
-<td>.nvd, .nvm</td>
-<td>Encodes length and boost factors for docs and fields</td>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.codecs.lucene42.Lucene42DocValuesFormat Per-Document Values}</td>
-<td>.dvd, .dvm</td>
-<td>Encodes additional scoring factors or other per-document information.</td>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.codecs.lucene42.Lucene42TermVectorsFormat Term Vector Index}</td>
-<td>.tvx</td>
-<td>Stores offset into the document data file</td>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.codecs.lucene42.Lucene42TermVectorsFormat Term Vector Documents}</td>
-<td>.tvd</td>
-<td>Contains information about each document that has term vectors</td>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.codecs.lucene42.Lucene42TermVectorsFormat Term Vector Fields}</td>
-<td>.tvf</td>
-<td>The field level info about term vectors</td>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.codecs.lucene40.Lucene40LiveDocsFormat Deleted Documents}</td>
-<td>.del</td>
-<td>Info about what files are deleted</td>
-</tr>
-</table>
-</div>
-<a name="Lock_File" id="Lock_File"></a>
-<h2>Lock File</h2>
-The write lock, which is stored in the index directory by default, is named
-"write.lock". If the lock directory is different from the index directory then
-the write lock will be named "XXXX-write.lock" where XXXX is a unique prefix
-derived from the full path to the index directory. When this file is present, a
-writer is currently modifying the index (adding or removing documents). This
-lock file ensures that only one writer is modifying the index at a time.</p>
-<a name="History"></a>
-<h2>History</h2>
-<p>Compatibility notes are provided in this document, describing how file
-formats have changed from prior versions:</p>
-<ul>
-<li>In version 2.1, the file format was changed to allow lock-less commits (ie,
-no more commit lock). The change is fully backwards compatible: you can open a
-pre-2.1 index for searching or adding/deleting of docs. When the new segments
-file is saved (committed), it will be written in the new file format (meaning
-no specific "upgrade" process is needed). But note that once a commit has
-occurred, pre-2.1 Lucene will not be able to read the index.</li>
-<li>In version 2.3, the file format was changed to allow segments to share a
-single set of doc store (vectors & stored fields) files. This allows for
-faster indexing in certain cases. The change is fully backwards compatible (in
-the same way as the lock-less commits change in 2.1).</li>
-<li>In version 2.4, Strings are now written as true UTF-8 byte sequence, not
-Java's modified UTF-8. See <a href="http://issues.apache.org/jira/browse/LUCENE-510">
-LUCENE-510</a> for details.</li>
-<li>In version 2.9, an optional opaque Map<String,String> CommitUserData
-may be passed to IndexWriter's commit methods (and later retrieved), which is
-recorded in the segments_N file. See <a href="http://issues.apache.org/jira/browse/LUCENE-1382">
-LUCENE-1382</a> for details. Also,
-diagnostics were added to each segment written recording details about why it
-was written (due to flush, merge; which OS/JRE was used; etc.). See issue
-<a href="http://issues.apache.org/jira/browse/LUCENE-1654">LUCENE-1654</a> for details.</li>
-<li>In version 3.0, compressed fields are no longer written to the index (they
-can still be read, but on merge the new segment will write them, uncompressed).
-See issue <a href="http://issues.apache.org/jira/browse/LUCENE-1960">LUCENE-1960</a>
-for details.</li>
-<li>In version 3.1, segments records the code version that created them. See
-<a href="http://issues.apache.org/jira/browse/LUCENE-2720">LUCENE-2720</a> for details.
-Additionally segments track explicitly whether or not they have term vectors.
-See <a href="http://issues.apache.org/jira/browse/LUCENE-2811">LUCENE-2811</a>
-for details.</li>
-<li>In version 3.2, numeric fields are written as natively to stored fields
-file, previously they were stored in text format only.</li>
-<li>In version 3.4, fields can omit position data while still indexing term
-frequencies.</li>
-<li>In version 4.0, the format of the inverted index became extensible via
-the {@link org.apache.lucene.codecs.Codec Codec} api. Fast per-document storage
-({@code DocValues}) was introduced. Normalization factors need no longer be a
-single byte, they can be any {@link org.apache.lucene.index.NumericDocValues NumericDocValues}.
-Terms need not be unicode strings, they can be any byte sequence. Term offsets
-can optionally be indexed into the postings lists. Payloads can be stored in the
-term vectors.</li>
-<li>In version 4.1, the format of the postings list changed to use either
-of FOR compression or variable-byte encoding, depending upon the frequency
-of the term. Terms appearing only once were changed to inline directly into
-the term dictionary. Stored fields are compressed by default. </li>
-<li>In version 4.2, term vectors are compressed by default. DocValues has
-a new multi-valued type (SortedSet), that can be used for faceting/grouping/joining
-on multi-valued fields.</li>
-<li>In version 4.5, DocValues were extended to explicitly represent missing values.</li>
-<li>In version 4.6, FieldInfos were extended to support per-field DocValues generation, to
-allow updating NumericDocValues fields.</li>
-<li>In version 4.8, checksum footers were added to the end of each index file
-for improved data integrity. Specifically, the last 8 bytes of every index file
-contain the zlib-crc32 checksum of the file.</li>
-</ul>
-<a name="Limitations" id="Limitations"></a>
-<h2>Limitations</h2>
-<div>
-<p>Lucene uses a Java <code>int</code> to refer to
-document numbers, and the index file format uses an <code>Int32</code>
-on-disk to store document numbers. This is a limitation
-of both the index file format and the current implementation. Eventually these
-should be replaced with either <code>UInt64</code> values, or
-better yet, {@link org.apache.lucene.store.DataOutput#writeVInt VInt} values which have no limit.</p>
-</div>
</body>
</html>
Modified: lucene/dev/branches/lucene5858/lucene/core/src/java/org/apache/lucene/codecs/lucene49/package.html
URL: http://svn.apache.org/viewvc/lucene/dev/branches/lucene5858/lucene/core/src/java/org/apache/lucene/codecs/lucene49/package.html?rev=1621770&r1=1621769&r2=1621770&view=diff
==============================================================================
--- lucene/dev/branches/lucene5858/lucene/core/src/java/org/apache/lucene/codecs/lucene49/package.html (original)
+++ lucene/dev/branches/lucene5858/lucene/core/src/java/org/apache/lucene/codecs/lucene49/package.html Mon Sep 1 13:31:12 2014
@@ -21,384 +21,5 @@
</head>
<body>
Lucene 4.9 file format.
-
-<h1>Apache Lucene - Index File Formats</h1>
-<div>
-<ul>
-<li><a href="#Introduction">Introduction</a></li>
-<li><a href="#Definitions">Definitions</a>
- <ul>
- <li><a href="#Inverted_Indexing">Inverted Indexing</a></li>
- <li><a href="#Types_of_Fields">Types of Fields</a></li>
- <li><a href="#Segments">Segments</a></li>
- <li><a href="#Document_Numbers">Document Numbers</a></li>
- </ul>
-</li>
-<li><a href="#Overview">Index Structure Overview</a></li>
-<li><a href="#File_Naming">File Naming</a></li>
-<li><a href="#file-names">Summary of File Extensions</a></li>
- <ul>
- <li><a href="#Lock_File">Lock File</a></li>
- <li><a href="#History">History</a></li>
- <li><a href="#Limitations">Limitations</a></li>
- </ul>
-</ul>
-</div>
-<a name="Introduction"></a>
-<h2>Introduction</h2>
-<div>
-<p>This document defines the index file formats used in this version of Lucene.
-If you are using a different version of Lucene, please consult the copy of
-<code>docs/</code> that was distributed with
-the version you are using.</p>
-<p>Apache Lucene is written in Java, but several efforts are underway to write
-<a href="http://wiki.apache.org/lucene-java/LuceneImplementations">versions of
-Lucene in other programming languages</a>. If these versions are to remain
-compatible with Apache Lucene, then a language-independent definition of the
-Lucene index format is required. This document thus attempts to provide a
-complete and independent definition of the Apache Lucene file formats.</p>
-<p>As Lucene evolves, this document should evolve. Versions of Lucene in
-different programming languages should endeavor to agree on file formats, and
-generate new versions of this document.</p>
-</div>
-<a name="Definitions" id="Definitions"></a>
-<h2>Definitions</h2>
-<div>
-<p>The fundamental concepts in Lucene are index, document, field and term.</p>
-<p>An index contains a sequence of documents.</p>
-<ul>
-<li>A document is a sequence of fields.</li>
-<li>A field is a named sequence of terms.</li>
-<li>A term is a sequence of bytes.</li>
-</ul>
-<p>The same sequence of bytes in two different fields is considered a different
-term. Thus terms are represented as a pair: the string naming the field, and the
-bytes within the field.</p>
-<a name="Inverted_Indexing"></a>
-<h3>Inverted Indexing</h3>
-<p>The index stores statistics about terms in order to make term-based search
-more efficient. Lucene's index falls into the family of indexes known as an
-<i>inverted index.</i> This is because it can list, for a term, the documents
-that contain it. This is the inverse of the natural relationship, in which
-documents list terms.</p>
-<a name="Types_of_Fields"></a>
-<h3>Types of Fields</h3>
-<p>In Lucene, fields may be <i>stored</i>, in which case their text is stored
-in the index literally, in a non-inverted manner. Fields that are inverted are
-called <i>indexed</i>. A field may be both stored and indexed.</p>
-<p>The text of a field may be <i>tokenized</i> into terms to be indexed, or the
-text of a field may be used literally as a term to be indexed. Most fields are
-tokenized, but sometimes it is useful for certain identifier fields to be
-indexed literally.</p>
-<p>See the {@link org.apache.lucene.document.Field Field}
-java docs for more information on Fields.</p>
-<a name="Segments" id="Segments"></a>
-<h3>Segments</h3>
-<p>Lucene indexes may be composed of multiple sub-indexes, or <i>segments</i>.
-Each segment is a fully independent index, which could be searched separately.
-Indexes evolve by:</p>
-<ol>
-<li>Creating new segments for newly added documents.</li>
-<li>Merging existing segments.</li>
-</ol>
-<p>Searches may involve multiple segments and/or multiple indexes, each index
-potentially composed of a set of segments.</p>
-<a name="Document_Numbers"></a>
-<h3>Document Numbers</h3>
-<p>Internally, Lucene refers to documents by an integer <i>document number</i>.
-The first document added to an index is numbered zero, and each subsequent
-document added gets a number one greater than the previous.</p>
-<p>Note that a document's number may change, so caution should be taken when
-storing these numbers outside of Lucene. In particular, numbers may change in
-the following situations:</p>
-<ul>
-<li>
-<p>The numbers stored in each segment are unique only within the segment, and
-must be converted before they can be used in a larger context. The standard
-technique is to allocate each segment a range of values, based on the range of
-numbers used in that segment. To convert a document number from a segment to an
-external value, the segment's <i>base</i> document number is added. To convert
-an external value back to a segment-specific value, the segment is identified
-by the range that the external value is in, and the segment's base value is
-subtracted. For example two five document segments might be combined, so that
-the first segment has a base value of zero, and the second of five. Document
-three from the second segment would have an external value of eight.</p>
-</li>
-<li>
-<p>When documents are deleted, gaps are created in the numbering. These are
-eventually removed as the index evolves through merging. Deleted documents are
-dropped when segments are merged. A freshly-merged segment thus has no gaps in
-its numbering.</p>
-</li>
-</ul>
-</div>
-<a name="Overview" id="Overview"></a>
-<h2>Index Structure Overview</h2>
-<div>
-<p>Each segment index maintains the following:</p>
-<ul>
-<li>
-{@link org.apache.lucene.codecs.lucene46.Lucene46SegmentInfoFormat Segment info}.
- This contains metadata about a segment, such as the number of documents,
- what files it uses,
-</li>
-<li>
-{@link org.apache.lucene.codecs.lucene46.Lucene46FieldInfosFormat Field names}.
- This contains the set of field names used in the index.
-</li>
-<li>
-{@link org.apache.lucene.codecs.lucene41.Lucene41StoredFieldsFormat Stored Field values}.
-This contains, for each document, a list of attribute-value pairs, where the attributes
-are field names. These are used to store auxiliary information about the document, such as
-its title, url, or an identifier to access a database. The set of stored fields are what is
-returned for each hit when searching. This is keyed by document number.
-</li>
-<li>
-{@link org.apache.lucene.codecs.lucene41.Lucene41PostingsFormat Term dictionary}.
-A dictionary containing all of the terms used in all of the
-indexed fields of all of the documents. The dictionary also contains the number
-of documents which contain the term, and pointers to the term's frequency and
-proximity data.
-</li>
-<li>
-{@link org.apache.lucene.codecs.lucene41.Lucene41PostingsFormat Term Frequency data}.
-For each term in the dictionary, the numbers of all the
-documents that contain that term, and the frequency of the term in that
-document, unless frequencies are omitted (IndexOptions.DOCS_ONLY)
-</li>
-<li>
-{@link org.apache.lucene.codecs.lucene41.Lucene41PostingsFormat Term Proximity data}.
-For each term in the dictionary, the positions that the
-term occurs in each document. Note that this will not exist if all fields in
-all documents omit position data.
-</li>
-<li>
-{@link org.apache.lucene.codecs.lucene49.Lucene49NormsFormat Normalization factors}.
-For each field in each document, a value is stored
-that is multiplied into the score for hits on that field.
-</li>
-<li>
-{@link org.apache.lucene.codecs.lucene42.Lucene42TermVectorsFormat Term Vectors}.
-For each field in each document, the term vector (sometimes
-called document vector) may be stored. A term vector consists of term text and
-term frequency. To add Term Vectors to your index see the
-{@link org.apache.lucene.document.Field Field} constructors
-</li>
-<li>
-{@link org.apache.lucene.codecs.lucene49.Lucene49DocValuesFormat Per-document values}.
-Like stored values, these are also keyed by document
-number, but are generally intended to be loaded into main memory for fast
-access. Whereas stored values are generally intended for summary results from
-searches, per-document values are useful for things like scoring factors.
-</li>
-<li>
-{@link org.apache.lucene.codecs.lucene40.Lucene40LiveDocsFormat Deleted documents}.
-An optional file indicating which documents are deleted.
-</li>
-</ul>
-<p>Details on each of these are provided in their linked pages.</p>
-</div>
-<a name="File_Naming"></a>
-<h2>File Naming</h2>
-<div>
-<p>All files belonging to a segment have the same name with varying extensions.
-The extensions correspond to the different file formats described below. When
-using the Compound File format (default in 1.4 and greater) these files (except
-for the Segment info file, the Lock file, and Deleted documents file) are collapsed
-into a single .cfs file (see below for details)</p>
-<p>Typically, all segments in an index are stored in a single directory,
-although this is not required.</p>
-<p>As of version 2.1 (lock-less commits), file names are never re-used (there
-is one exception, "segments.gen", see below). That is, when any file is saved
-to the Directory it is given a never before used filename. This is achieved
-using a simple generations approach. For example, the first segments file is
-segments_1, then segments_2, etc. The generation is a sequential long integer
-represented in alpha-numeric (base 36) form.</p>
-</div>
-<a name="file-names" id="file-names"></a>
-<h2>Summary of File Extensions</h2>
-<div>
-<p>The following table summarizes the names and extensions of the files in
-Lucene:</p>
-<table cellspacing="1" cellpadding="4">
-<tr>
-<th>Name</th>
-<th>Extension</th>
-<th>Brief Description</th>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.index.SegmentInfos Segments File}</td>
-<td>segments.gen, segments_N</td>
-<td>Stores information about a commit point</td>
-</tr>
-<tr>
-<td><a href="#Lock_File">Lock File</a></td>
-<td>write.lock</td>
-<td>The Write lock prevents multiple IndexWriters from writing to the same
-file.</td>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.codecs.lucene40.Lucene40SegmentInfoFormat Segment Info}</td>
-<td>.si</td>
-<td>Stores metadata about a segment</td>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.store.CompoundFileDirectory Compound File}</td>
-<td>.cfs, .cfe</td>
-<td>An optional "virtual" file consisting of all the other index files for
-systems that frequently run out of file handles.</td>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.codecs.lucene46.Lucene46FieldInfosFormat Fields}</td>
-<td>.fnm</td>
-<td>Stores information about the fields</td>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.codecs.lucene41.Lucene41StoredFieldsFormat Field Index}</td>
-<td>.fdx</td>
-<td>Contains pointers to field data</td>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.codecs.lucene41.Lucene41StoredFieldsFormat Field Data}</td>
-<td>.fdt</td>
-<td>The stored fields for documents</td>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.codecs.lucene41.Lucene41PostingsFormat Term Dictionary}</td>
-<td>.tim</td>
-<td>The term dictionary, stores term info</td>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.codecs.lucene41.Lucene41PostingsFormat Term Index}</td>
-<td>.tip</td>
-<td>The index into the Term Dictionary</td>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.codecs.lucene41.Lucene41PostingsFormat Frequencies}</td>
-<td>.doc</td>
-<td>Contains the list of docs which contain each term along with frequency</td>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.codecs.lucene41.Lucene41PostingsFormat Positions}</td>
-<td>.pos</td>
-<td>Stores position information about where a term occurs in the index</td>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.codecs.lucene41.Lucene41PostingsFormat Payloads}</td>
-<td>.pay</td>
-<td>Stores additional per-position metadata information such as character offsets and user payloads</td>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.codecs.lucene49.Lucene49NormsFormat Norms}</td>
-<td>.nvd, .nvm</td>
-<td>Encodes length and boost factors for docs and fields</td>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.codecs.lucene49.Lucene49DocValuesFormat Per-Document Values}</td>
-<td>.dvd, .dvm</td>
-<td>Encodes additional scoring factors or other per-document information.</td>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.codecs.lucene42.Lucene42TermVectorsFormat Term Vector Index}</td>
-<td>.tvx</td>
-<td>Stores offset into the document data file</td>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.codecs.lucene42.Lucene42TermVectorsFormat Term Vector Documents}</td>
-<td>.tvd</td>
-<td>Contains information about each document that has term vectors</td>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.codecs.lucene42.Lucene42TermVectorsFormat Term Vector Fields}</td>
-<td>.tvf</td>
-<td>The field level info about term vectors</td>
-</tr>
-<tr>
-<td>{@link org.apache.lucene.codecs.lucene40.Lucene40LiveDocsFormat Deleted Documents}</td>
-<td>.del</td>
-<td>Info about what files are deleted</td>
-</tr>
-</table>
-</div>
-<a name="Lock_File" id="Lock_File"></a>
-<h2>Lock File</h2>
-The write lock, which is stored in the index directory by default, is named
-"write.lock". If the lock directory is different from the index directory then
-the write lock will be named "XXXX-write.lock" where XXXX is a unique prefix
-derived from the full path to the index directory. When this file is present, a
-writer is currently modifying the index (adding or removing documents). This
-lock file ensures that only one writer is modifying the index at a time.</p>
-<a name="History"></a>
-<h2>History</h2>
-<p>Compatibility notes are provided in this document, describing how file
-formats have changed from prior versions:</p>
-<ul>
-<li>In version 2.1, the file format was changed to allow lock-less commits (ie,
-no more commit lock). The change is fully backwards compatible: you can open a
-pre-2.1 index for searching or adding/deleting of docs. When the new segments
-file is saved (committed), it will be written in the new file format (meaning
-no specific "upgrade" process is needed). But note that once a commit has
-occurred, pre-2.1 Lucene will not be able to read the index.</li>
-<li>In version 2.3, the file format was changed to allow segments to share a
-single set of doc store (vectors & stored fields) files. This allows for
-faster indexing in certain cases. The change is fully backwards compatible (in
-the same way as the lock-less commits change in 2.1).</li>
-<li>In version 2.4, Strings are now written as true UTF-8 byte sequence, not
-Java's modified UTF-8. See <a href="http://issues.apache.org/jira/browse/LUCENE-510">
-LUCENE-510</a> for details.</li>
-<li>In version 2.9, an optional opaque Map<String,String> CommitUserData
-may be passed to IndexWriter's commit methods (and later retrieved), which is
-recorded in the segments_N file. See <a href="http://issues.apache.org/jira/browse/LUCENE-1382">
-LUCENE-1382</a> for details. Also,
-diagnostics were added to each segment written recording details about why it
-was written (due to flush, merge; which OS/JRE was used; etc.). See issue
-<a href="http://issues.apache.org/jira/browse/LUCENE-1654">LUCENE-1654</a> for details.</li>
-<li>In version 3.0, compressed fields are no longer written to the index (they
-can still be read, but on merge the new segment will write them, uncompressed).
-See issue <a href="http://issues.apache.org/jira/browse/LUCENE-1960">LUCENE-1960</a>
-for details.</li>
-<li>In version 3.1, segments records the code version that created them. See
-<a href="http://issues.apache.org/jira/browse/LUCENE-2720">LUCENE-2720</a> for details.
-Additionally segments track explicitly whether or not they have term vectors.
-See <a href="http://issues.apache.org/jira/browse/LUCENE-2811">LUCENE-2811</a>
-for details.</li>
-<li>In version 3.2, numeric fields are written as natively to stored fields
-file, previously they were stored in text format only.</li>
-<li>In version 3.4, fields can omit position data while still indexing term
-frequencies.</li>
-<li>In version 4.0, the format of the inverted index became extensible via
-the {@link org.apache.lucene.codecs.Codec Codec} api. Fast per-document storage
-({@code DocValues}) was introduced. Normalization factors need no longer be a
-single byte, they can be any {@link org.apache.lucene.index.NumericDocValues NumericDocValues}.
-Terms need not be unicode strings, they can be any byte sequence. Term offsets
-can optionally be indexed into the postings lists. Payloads can be stored in the
-term vectors.</li>
-<li>In version 4.1, the format of the postings list changed to use either
-of FOR compression or variable-byte encoding, depending upon the frequency
-of the term. Terms appearing only once were changed to inline directly into
-the term dictionary. Stored fields are compressed by default. </li>
-<li>In version 4.2, term vectors are compressed by default. DocValues has
-a new multi-valued type (SortedSet), that can be used for faceting/grouping/joining
-on multi-valued fields.</li>
-<li>In version 4.5, DocValues were extended to explicitly represent missing values.</li>
-<li>In version 4.6, FieldInfos were extended to support per-field DocValues generation, to
-allow updating NumericDocValues fields.</li>
-<li>In version 4.8, checksum footers were added to the end of each index file
-for improved data integrity. Specifically, the last 8 bytes of every index file
-contain the zlib-crc32 checksum of the file.</li>
-<li>In version 4.9, DocValues has a new multi-valued numeric type (SortedNumeric)
-that is suitable for faceting/sorting/analytics.
-</li>
-</ul>
-<a name="Limitations" id="Limitations"></a>
-<h2>Limitations</h2>
-<div>
-<p>Lucene uses a Java <code>int</code> to refer to
-document numbers, and the index file format uses an <code>Int32</code>
-on-disk to store document numbers. This is a limitation
-of both the index file format and the current implementation. Eventually these
-should be replaced with either <code>UInt64</code> values, or
-better yet, {@link org.apache.lucene.store.DataOutput#writeVInt VInt} values which have no limit.</p>
-</div>
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