https://lucene.apache.org/lucene-parent/lucene-core: Apache Lucene Java Core (The Apache Software Foundation) 
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Codecs API: API for customization of the encoding and structure of the index.


  The Codec API allows you to customise the way the following pieces of index information are stored:


 
  For some concrete implementations beyond Lucene's official index format, see
  the Codecs module.

 Codecs are identified by name through the Java Service Provider Interface. To create your own codec, extend Codec and pass the new codec's name to the super() constructor: 
public class MyCodec extends Codec {
    public MyCodec() {
        super("MyCodecName");
    }
    ...
}

 You will need to register the Codec class so that the ServiceLoader can find it, by including a META-INF/services/org.apache.lucene.codecs.Codec file on your classpath that contains the package-qualified name of your codec. 
 If you just want to customise the PostingsFormat, or use different postings formats for different fields, then you can register your custom postings format in the same way (in META-INF/services/org.apache.lucene.codecs.PostingsFormat), and then extend the default codec and override org.apache.lucene.codecs.luceneMN.LuceneMNCodec#getPostingsFormatForField(String) to return your custom postings format. 


 Similarly, if you just want to customise the DocValuesFormat per-field, have a look at LuceneMNCodec.getDocValuesFormatForField(String). 


/**
 * Codecs API: API for customization of the encoding and structure of the index.
 * 
 * <p>
 *   The Codec API allows you to customise the way the following pieces of index information are stored:
 * <ul>
 *   <li>Postings lists - see {@link org.apache.lucene.codecs.PostingsFormat}</li>
 *   <li>DocValues - see {@link org.apache.lucene.codecs.DocValuesFormat}</li>
 *   <li>Stored fields - see {@link org.apache.lucene.codecs.StoredFieldsFormat}</li>
 *   <li>Term vectors - see {@link org.apache.lucene.codecs.TermVectorsFormat}</li>
 *   <li>Points - see {@link org.apache.lucene.codecs.PointsFormat}</li>
 *   <li>FieldInfos - see {@link org.apache.lucene.codecs.FieldInfosFormat}</li>
 *   <li>SegmentInfo - see {@link org.apache.lucene.codecs.SegmentInfoFormat}</li>
 *   <li>Norms - see {@link org.apache.lucene.codecs.NormsFormat}</li>
 *   <li>Live documents - see {@link org.apache.lucene.codecs.LiveDocsFormat}</li>
 * </ul>
 *  
 *   For some concrete implementations beyond Lucene's official index format, see
 *   the <a href="{@docRoot}/../codecs/overview-summary.html">Codecs module</a>.
 * 
 * <p>
 *   Codecs are identified by name through the Java Service Provider Interface.  To create your own codec, extend
 *   {@link org.apache.lucene.codecs.Codec} and pass the new codec's name to the super() constructor:
 * <pre class="prettyprint">
 * public class MyCodec extends Codec {
 * 
 *     public MyCodec() {
 *         super("MyCodecName");
 *     }
 * 
 *     ...
 * }
 * </pre>
 * You will need to register the Codec class so that the {@link java.util.ServiceLoader ServiceLoader} can find it, by including a
 * META-INF/services/org.apache.lucene.codecs.Codec file on your classpath that contains the package-qualified
 * name of your codec.
 * 
 * <p>
 *   If you just want to customise the {@link org.apache.lucene.codecs.PostingsFormat}, or use different postings
 *   formats for different fields, then you can register your custom postings format in the same way (in
 *   META-INF/services/org.apache.lucene.codecs.PostingsFormat), and then extend the default
 *   codec and override
 *   {@code org.apache.lucene.codecs.luceneMN.LuceneMNCodec#getPostingsFormatForField(String)} to return your custom
 *   postings format.
 * </p>
 * <p>
 *   Similarly, if you just want to customise the {@link org.apache.lucene.codecs.DocValuesFormat} per-field, have 
 *   a look at {@code LuceneMNCodec.getDocValuesFormatForField(String)}.
 * </p>
 */
package org.apache.lucene.codecs;