lucene/codecs/src/java/org/apache/lucene/codecs/uniformsplit/sharedterms/STMergingBlockReader.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.uniformsplit.sharedterms;

import java.io.IOException;
import java.util.Map;
import org.apache.lucene.codecs.BlockTermState;
import org.apache.lucene.codecs.PostingsReaderBase;
import org.apache.lucene.codecs.uniformsplit.BlockDecoder;
import org.apache.lucene.codecs.uniformsplit.FieldMetadata;
import org.apache.lucene.codecs.uniformsplit.IndexDictionary;
import org.apache.lucene.index.FieldInfos;
import org.apache.lucene.index.PostingsEnum;
import org.apache.lucene.index.TermState;
import org.apache.lucene.store.IndexInput;
import org.apache.lucene.util.BytesRef;

/**
 * {@link org.apache.lucene.index.TermsEnum} used when merging segments, to enumerate the terms of
 * an input segment and get all the fields {@link TermState}s of each term.
 *
 * <p>It only supports calls to {@link #next()} and no seek method.
 *
 * @lucene.experimental
 */
public class STMergingBlockReader extends STBlockReader {

  public STMergingBlockReader(
      IndexDictionary.BrowserSupplier dictionaryBrowserSupplier,
      IndexInput blockInput,
      PostingsReaderBase postingsReader,
      FieldMetadata fieldMetadata,
      BlockDecoder blockDecoder,
      FieldInfos fieldInfos)
      throws IOException {
    super(
        dictionaryBrowserSupplier,
        blockInput,
        postingsReader,
        fieldMetadata,
        blockDecoder,
        fieldInfos);
  }

  @Override
  public SeekStatus seekCeil(BytesRef searchedTerm) {
    throw new UnsupportedOperationException();
  }

  @Override
  public boolean seekExact(BytesRef searchedTerm) {
    throw new UnsupportedOperationException();
  }

  @Override
  public void seekExact(BytesRef term, TermState state) {
    throw new UnsupportedOperationException();
  }

  @Override
  public void seekExact(long ord) {
    throw new UnsupportedOperationException();
  }

  @Override
  protected BlockTermState readTermStateIfNotRead() {
    throw new UnsupportedOperationException();
  }

  @Override
  public BytesRef next() throws IOException {
    return nextTerm();
  }

  /**
   * Creates a new {@link PostingsEnum} for the provided field and {@link BlockTermState}.
   *
   * @param reuse Previous {@link PostingsEnum} to reuse; or null to create a new one.
   * @param flags Postings flags.
   */
  public PostingsEnum postings(
      String fieldName, BlockTermState termState, PostingsEnum reuse, int flags)
      throws IOException {
    return postingsReader.postings(fieldInfos.fieldInfo(fieldName), termState, reuse, flags);
  }

  /**
   * Reads all the fields {@link TermState}s of the current term and put them in the provided map.
   * Clears the map first, before putting {@link TermState}s.
   */
  public void readFieldTermStatesMap(Map<String, BlockTermState> fieldTermStatesMap)
      throws IOException {
    if (term() != null) {
      termStatesReadBuffer.setPosition(
          blockFirstLineStart
              + blockHeader.getTermStatesBaseOffset()
              + blockLine.getTermStateRelativeOffset());
      ((STBlockLine.Serializer) blockLineReader)
          .readFieldTermStatesMap(
              termStatesReadBuffer,
              termStateSerializer,
              blockHeader,
              fieldInfos,
              fieldTermStatesMap);
    }
  }
}