the-algorithm/src/java/com/twitter/search/earlybird/segment/EmptySegmentDataReaderSet.java

package com.twitter.search.earlybird.segment;

import java.util.Optional;

import com.twitter.search.common.indexing.thriftjava.ThriftVersionedEvents;
import com.twitter.search.common.util.io.EmptyRecordReader;
import com.twitter.search.common.util.io.recordreader.RecordReader;
import com.twitter.search.earlybird.document.TweetDocument;
import com.twitter.search.earlybird.partition.SegmentInfo;

/**
 * A SegmentDataReaderSet that returns no data. Uses a DocumentReader that is
 * always caught up, but never gets exhausted.
 * Can be used for bringing up an earlybird against a static set of segments,
 * and will not incorporate any new updates.
 */
public class EmptySegmentDataReaderSet implements SegmentDataReaderSet {
  public static final EmptySegmentDataReaderSet INSTANCE = new EmptySegmentDataReaderSet();

  @Override
  public void attachDocumentReaders(SegmentInfo segmentInfo) {
  }

  @Override
  public void attachUpdateReaders(SegmentInfo segmentInfo) {
  }

  @Override
  public void completeSegmentDocs(SegmentInfo segmentInfo) {
  }

  @Override
  public void stopSegmentUpdates(SegmentInfo segmentInfo) {
  }

  @Override
  public void stopAll() {
  }

  @Override
  public boolean allCaughtUp() {
    // ALWAYS CAUGHT UP
    return true;
  }

  @Override
  public RecordReader<TweetDocument> newDocumentReader(SegmentInfo segmentInfo)
      throws Exception {
    return null;
  }

  @Override
  public RecordReader<TweetDocument> getDocumentReader() {
    return new EmptyRecordReader<>();
  }

  @Override
  public RecordReader<ThriftVersionedEvents> getUpdateEventsReader() {
    return null;
  }

  @Override
  public RecordReader<ThriftVersionedEvents> getUpdateEventsReaderForSegment(
      SegmentInfo segmentInfo) {
    return null;
  }

  @Override
  public Optional<Long> getUpdateEventsStreamOffsetForSegment(SegmentInfo segmentInfo) {
    return Optional.of(0L);
  }
}