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 {@link org.apache.lucene.codecs.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 {@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.

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 {@link org.apache.lucene.codecs.lucene49.Lucene49Codec} and override {@link org.apache.lucene.codecs.lucene49.Lucene49Codec#getPostingsFormatForField(String)} to return your custom postings format.

Similarly, if you just want to customise the {@link org.apache.lucene.codecs.DocValuesFormat} per-field, have a look at {@link org.apache.lucene.codecs.lucene49.Lucene49Codec#getDocValuesFormatForField(String)}.