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A module that is everything required to understands Druid Segments

There is a newer version: 0.12.3

/*
 * Licensed to Metamarkets Group Inc. (Metamarkets) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. Metamarkets 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 io.druid.segment;

import com.google.common.base.Strings;
import com.google.common.collect.Iterators;
import io.druid.segment.data.IndexedInts;

import java.io.IOException;
import java.util.Iterator;

public class NullDimensionSelector implements DimensionSelector
{

  private static final IndexedInts SINGLETON = new IndexedInts() {
    @Override
    public int size() {
      return 1;
    }

    @Override
    public int get(int index) {
      return 0;
    }

    @Override
    public Iterator iterator() {
      return Iterators.singletonIterator(0);
    }

    @Override
    public void fill(int index, int[] toFill)
    {
      throw new UnsupportedOperationException("NullDimensionSelector does not support fill");
    }

    @Override
    public void close() throws IOException
    {

    }
  };

  @Override
  public IndexedInts getRow()
  {
    return SINGLETON;
  }

  @Override
  public int getValueCardinality()
  {
    return 1;
  }

  @Override
  public String lookupName(int id)
  {
    return null;
  }

  @Override
  public int lookupId(String name)
  {
    return Strings.isNullOrEmpty(name) ? 0 : -1;
  }
}