lucene-commits mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From mikemcc...@apache.org
Subject lucene-solr:branch_6x: LUCENE-7532: add back lost codec file format documentation
Date Tue, 01 Nov 2016 18:00:12 GMT
Repository: lucene-solr
Updated Branches:
  refs/heads/branch_6x 8c42045f2 -> 830a3fdfb


LUCENE-7532: add back lost codec file format documentation


Project: http://git-wip-us.apache.org/repos/asf/lucene-solr/repo
Commit: http://git-wip-us.apache.org/repos/asf/lucene-solr/commit/830a3fdf
Tree: http://git-wip-us.apache.org/repos/asf/lucene-solr/tree/830a3fdf
Diff: http://git-wip-us.apache.org/repos/asf/lucene-solr/diff/830a3fdf

Branch: refs/heads/branch_6x
Commit: 830a3fdfbf12553d47f8f6c320c862aa88fdc48b
Parents: 8c42045
Author: Mike McCandless <mikemccand@apache.org>
Authored: Tue Nov 1 14:00:00 2016 -0400
Committer: Mike McCandless <mikemccand@apache.org>
Committed: Tue Nov 1 14:00:00 2016 -0400

----------------------------------------------------------------------
 lucene/CHANGES.txt                              |   6 +
 .../lucene/codecs/lucene62/package-info.java    | 400 ++++++++++++++++++-
 2 files changed, 402 insertions(+), 4 deletions(-)
----------------------------------------------------------------------


http://git-wip-us.apache.org/repos/asf/lucene-solr/blob/830a3fdf/lucene/CHANGES.txt
----------------------------------------------------------------------
diff --git a/lucene/CHANGES.txt b/lucene/CHANGES.txt
index 34b62d3..0bfb1ad 100644
--- a/lucene/CHANGES.txt
+++ b/lucene/CHANGES.txt
@@ -6,6 +6,12 @@ http://s.apache.org/luceneversions
 ======================= Lucene 6.4.0 =======================
 (No Changes)
 
+Improvements
+
+* LUCENE-7532: Add back lost codec file format documentation
+  (Shinichiro Abe via Mike McCandless)
+
+
 ======================= Lucene 6.3.0 =======================
 
 API Changes

http://git-wip-us.apache.org/repos/asf/lucene-solr/blob/830a3fdf/lucene/core/src/java/org/apache/lucene/codecs/lucene62/package-info.java
----------------------------------------------------------------------
diff --git a/lucene/core/src/java/org/apache/lucene/codecs/lucene62/package-info.java b/lucene/core/src/java/org/apache/lucene/codecs/lucene62/package-info.java
index 2fe2dc7..170b7bf 100644
--- a/lucene/core/src/java/org/apache/lucene/codecs/lucene62/package-info.java
+++ b/lucene/core/src/java/org/apache/lucene/codecs/lucene62/package-info.java
@@ -16,9 +16,401 @@
  */
 
 /**
- * Components from the Lucene 6.2 index format
- * See {@link org.apache.lucene.codecs.lucene62} for an overview
- * of the index format.
+ * Lucene 6.2 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>
+ *   <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>
+ * </li>
+ * </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"></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"></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"></a>
+ * <h2>Index Structure Overview</h2>
+ * <div>
+ * <p>Each segment index maintains the following:</p>
+ * <ul>
+ * <li>
+ * {@link org.apache.lucene.codecs.lucene62.Lucene62SegmentInfoFormat 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.lucene50.Lucene50FieldInfosFormat Field names}. 
+ *    This contains the set of field names used in the index.
+ * </li>
+ * <li>
+ * {@link org.apache.lucene.codecs.lucene50.Lucene50StoredFieldsFormat 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.lucene50.Lucene50PostingsFormat 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.lucene50.Lucene50PostingsFormat 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.lucene50.Lucene50PostingsFormat 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.lucene53.Lucene53NormsFormat 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.lucene50.Lucene50TermVectorsFormat 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.lucene54.Lucene54DocValuesFormat 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.lucene50.Lucene50LiveDocsFormat Live documents}. 
+ * An optional file indicating which documents are live.
+ * </li>
+ * <li>
+ * {@link org.apache.lucene.codecs.lucene60.Lucene60PointsFormat Point values}.
+ * Optional pair of files, recording dimensionally indexed fields, to enable fast
+ * numeric range filtering and large numeric values like BigInteger and BigDecimal (1D)
+ * and geographic shape intersection (2D, 3D).
+ * </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.
+ * 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"></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" summary="lucene filenames by extension">
+ * <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_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.lucene62.Lucene62SegmentInfoFormat Segment Info}</td>
+ * <td>.si</td>
+ * <td>Stores metadata about a segment</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene50.Lucene50CompoundFormat 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.lucene50.Lucene50FieldInfosFormat Fields}</td>
+ * <td>.fnm</td>
+ * <td>Stores information about the fields</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene50.Lucene50StoredFieldsFormat Field Index}</td>
+ * <td>.fdx</td>
+ * <td>Contains pointers to field data</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene50.Lucene50StoredFieldsFormat Field Data}</td>
+ * <td>.fdt</td>
+ * <td>The stored fields for documents</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene50.Lucene50PostingsFormat Term Dictionary}</td>
+ * <td>.tim</td>
+ * <td>The term dictionary, stores term info</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene50.Lucene50PostingsFormat Term Index}</td>
+ * <td>.tip</td>
+ * <td>The index into the Term Dictionary</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene50.Lucene50PostingsFormat 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.lucene50.Lucene50PostingsFormat 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.lucene50.Lucene50PostingsFormat 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.lucene53.Lucene53NormsFormat 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.lucene54.Lucene54DocValuesFormat 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.lucene50.Lucene50TermVectorsFormat Term Vector
Index}</td>
+ * <td>.tvx</td>
+ * <td>Stores offset into the document data file</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene50.Lucene50TermVectorsFormat 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.lucene50.Lucene50TermVectorsFormat Term Vector
Fields}</td>
+ * <td>.tvf</td>
+ * <td>The field level info about term vectors</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene50.Lucene50LiveDocsFormat Live Documents}</td>
+ * <td>.liv</td>
+ * <td>Info about what files are live</td>
+ * </tr>
+ * <tr>
+ * <td>{@link org.apache.lucene.codecs.lucene60.Lucene60PointsFormat Point values}</td>
+ * <td>.dii, .dim</td>
+ * <td>Holds indexed points, if any</td>
+ * </tr>
+ * </table>
+ * </div>
+ * <a name="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.
+ * <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 &amp; 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&lt;String,String&gt; 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>In version 5.4, DocValues have been improved to store more information on disk:
+ * addresses for binary fields and ord indexes for multi-valued fields.
+ * <li>In version 6.0, Points were added, for multi-dimensional range/distance search.
+ * <li>In version 6.2, new Segment info format that reads/writes the index sort, to
support index sorting.
+ * </li>
+ * </ul>
+ * <a name="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>
  */
-
 package org.apache.lucene.codecs.lucene62;


Mime
View raw message