Package org.apache.lucene.analysis.tokenattributes

Interface TermToBytesRefAttribute

  • All Superinterfaces:
    Attribute
    All Known Implementing Classes:
    CharTermAttributeImpl, CollatedTermAttributeImpl, NumericTokenStream.NumericTermAttributeImpl, Token
    public interface TermToBytesRefAttribute
extends Attribute
    This attribute is requested by TermsHashPerField to index the contents. This attribute can be used to customize the final byte[] encoding of terms.

    Consumers of this attribute call getBytesRef() up-front, and then invoke fillBytesRef() for each term. Example: 

       final TermToBytesRefAttribute termAtt = tokenStream.getAttribute(TermToBytesRefAttribute.class);
   final BytesRef bytes = termAtt.getBytesRef();

   while (tokenStream.incrementToken() {

     // you must call termAtt.fillBytesRef() before doing something with the bytes.
     // this encodes the term value (internally it might be a char[], etc) into the bytes.
     int hashCode = termAtt.fillBytesRef();

     if (isInteresting(bytes)) {
     
       // because the bytes are reused by the attribute (like CharTermAttribute's char[] buffer),
       // you should make a copy if you need persistent access to the bytes, otherwise they will
       // be rewritten across calls to incrementToken()

       doSomethingWith(new BytesRef(bytes));
     }
   }
   ...

    • Method Detail

      • fillBytesRef

        int fillBytesRef()
        Updates the bytes getBytesRef() to contain this term's final encoding, and returns its hashcode.
        Returns:
        the hashcode as defined by BytesRef.hashCode(): 
          int hash = 0;
  for (int i = termBytes.offset; i < termBytes.offset+termBytes.length; i++) {
    hash = 31*hash + termBytes.bytes[i];
  }
        Implement this for performance reasons, if your code can calculate the hash on-the-fly. If this is not the case, just return termBytes.hashCode().

      • getBytesRef

        BytesRef getBytesRef()
        Retrieve this attribute's BytesRef. The bytes are updated from the current term when the consumer calls fillBytesRef().
        Returns:
        this Attributes internal BytesRef.