lucene/core/src/java/org/apache/lucene/codecs/PostingsWriterBase.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.lucene.codecs;

import java.io.Closeable;
import java.io.IOException;
import org.apache.lucene.codecs.lucene90.blocktree.Lucene90BlockTreeTermsWriter;
import org.apache.lucene.index.FieldInfo;
import org.apache.lucene.index.SegmentWriteState;
import org.apache.lucene.index.TermsEnum;
import org.apache.lucene.store.DataOutput;
import org.apache.lucene.store.IndexOutput;
import org.apache.lucene.util.BytesRef;
import org.apache.lucene.util.FixedBitSet;

/**
 * Class that plugs into term dictionaries, such as {@link Lucene90BlockTreeTermsWriter}, and
 * handles writing postings.
 *
 * @see PostingsReaderBase
 * @lucene.experimental
 */
// TODO: find a better name; this defines the API that the
// terms dict impls use to talk to a postings impl.
// TermsDict + PostingsReader/WriterBase == FieldsProducer/Consumer
public abstract class PostingsWriterBase implements Closeable {

  /** Sole constructor. (For invocation by subclass constructors, typically implicit.) */
  protected PostingsWriterBase() {}

  /**
   * Called once after startup, before any terms have been added. Implementations typically write a
   * header to the provided {@code termsOut}.
   */
  public abstract void init(IndexOutput termsOut, SegmentWriteState state) throws IOException;

  /**
   * Write all postings for one term; use the provided {@link TermsEnum} to pull a {@link
   * org.apache.lucene.index.PostingsEnum}. This method should not re-position the {@code
   * TermsEnum}! It is already positioned on the term that should be written. This method must set
   * the bit in the provided {@link FixedBitSet} for every docID written. If no docs were written,
   * this method should return null, and the terms dict will skip the term.
   */
  public abstract BlockTermState writeTerm(
      BytesRef term, TermsEnum termsEnum, FixedBitSet docsSeen, NormsProducer norms)
      throws IOException;

  /**
   * Encode metadata as long[] and byte[]. {@code absolute} controls whether current term is delta
   * encoded according to latest term. Usually elements in {@code longs} are file pointers, so each
   * one always increases when a new term is consumed. {@code out} is used to write generic bytes,
   * which are not monotonic.
   */
  public abstract void encodeTerm(
      DataOutput out, FieldInfo fieldInfo, BlockTermState state, boolean absolute)
      throws IOException;

  /** Sets the current field for writing. */
  public abstract void setField(FieldInfo fieldInfo);

  @Override
  public abstract void close() throws IOException;
}