processing/src/main/java/org/apache/druid/query/extraction/IdentityExtractionFn.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.druid.query.extraction;

import org.apache.druid.common.config.NullHandling;

import javax.annotation.Nullable;

public class IdentityExtractionFn implements ExtractionFn
{
  private static final IdentityExtractionFn INSTANCE = new IdentityExtractionFn();

  private IdentityExtractionFn()
  {

  }

  @Override
  public byte[] getCacheKey()
  {
    return new byte[]{ExtractionCacheHelper.CACHE_TYPE_ID_IDENTITY};
  }

  @Override
  @Nullable
  public String apply(@Nullable Object value)
  {
    return value == null ? null : NullHandling.emptyToNullIfNeeded(value.toString());
  }

  @Override
  @Nullable
  public String apply(@Nullable String value)
  {
    return NullHandling.emptyToNullIfNeeded(value);
  }

  @Override
  public String apply(long value)
  {
    return Long.toString(value);
  }

  @Override
  public boolean preservesOrdering()
  {
    return true;
  }

  @Override
  public ExtractionType getExtractionType()
  {
    return ExtractionType.ONE_TO_ONE;
  }

  @Override
  public String toString()
  {
    return "Identity";
  }

  @Override
  public boolean equals(Object o)
  {
    return o != null && o instanceof IdentityExtractionFn;
  }

  @Override
  public int hashCode()
  {
    return 0;
  }

  public static IdentityExtractionFn getInstance()
  {
    return INSTANCE;
  }
}