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.rel.hint;
  
  import org.apache.calcite.util.Litmus;
  
  /**
   * A {@code HintOptionChecker} validates the options of a {@link RelHint}.
   *
   * <p>Every hint would have a validation when converting to a {@link RelHint}, the
   * validation logic is: i) checks whether the hint was already registered;
   * ii) use the registered {@code HintOptionChecker} to check the hint options.
   *
   * <p>In {@link HintStrategyTable} the option checker is used for
   * hints registration as an optional parameter.
   *
   * @see HintStrategyTable#validateHint
   */
  @FunctionalInterface
  public interface HintOptionChecker {
    /**
     * Checks if the given hint is valid.
     *
     * <p>Always use the {@link Litmus#check(boolean, String, Object...)}
     * to do the check. The default behavior is to log warnings for any hint error.
     *
     * @param hint The hint to check
     * @param errorHandler The error handler
     *
     * @return True if the check passes
     */
    boolean checkOptions(RelHint hint, Litmus errorHandler);
  }
  