content: /*
   * 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.calcite.runtime.variant;
  
  import org.apache.calcite.runtime.rtti.RuntimeTypeInformation;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  /** The VARIANT type has its own notion of null, which is
   * different from the SQL NULL value.  For example, two variant nulls are equal
   * with each other.  This class represents such values. */
  public class VariantNull extends VariantValue {
    // Protected constructor to enforce a singleton pattern
    protected VariantNull() {}
  
    @Override public String getTypeString() {
      return "VARIANT";
    }
  
    @Override public @Nullable Object cast(RuntimeTypeInformation type) {
      // Result is always null
      return null;
    }
  
    @Override public @Nullable Object item(Object index) {
      // Result is always null
      return null;
    }
  
    public static final VariantNull INSTANCE = new VariantNull();
  
    /** Get the single instance of this type. */
    // Called from BuiltInMethod.VARIANTNULL
    public static VariantNull getInstance() {
      return INSTANCE;
    }
  
    @Override public int hashCode() {
      return 0;
    }
  
    @SuppressWarnings("EqualsWhichDoesntCheckParameterClass")
    @Override public boolean equals(@Nullable Object other) {
      return other == INSTANCE;
    }
  
    @Override public String toString() {
      return "null";
    }
  }
  