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A module that is everything required to understands Druid Segments

There is a newer version: 31.0.0

/*
 * 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.druid.query;

import org.apache.druid.java.util.common.guava.Sequence;
import org.apache.druid.java.util.common.guava.Sequences;
import org.apache.druid.query.context.ResponseContext;
import org.apache.druid.segment.SegmentReference;

public class ReferenceCountingSegmentQueryRunner implements QueryRunner
{
  private final QueryRunnerFactory> factory;
  private final SegmentReference segment;
  private final SegmentDescriptor descriptor;

  public ReferenceCountingSegmentQueryRunner(
      QueryRunnerFactory> factory,
      SegmentReference segment,
      SegmentDescriptor descriptor
  )
  {
    this.factory = factory;
    this.segment = segment;
    this.descriptor = descriptor;
  }

  @Override
  public Sequence run(final QueryPlus queryPlus, ResponseContext responseContext)
  {
    return segment.acquireReferences().map(closeable -> {
      try {
        final Sequence baseSequence = factory.createRunner(segment).run(queryPlus, responseContext);
        return Sequences.withBaggage(baseSequence, closeable);
      }
      catch (Throwable t) {
        try {
          closeable.close();
        }
        catch (Exception e) {
          t.addSuppressed(e);
        }
        throw t;
      }
    }).orElseGet(() -> new ReportTimelineMissingSegmentQueryRunner(descriptor).run(queryPlus, responseContext));
  }
}