/*
 * 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.spark.sql

import org.apache.spark.annotation.{Experimental, Unstable}
import org.apache.spark.sql.catalyst.plans.logical.LogicalPlan
import org.apache.spark.sql.catalyst.rules.Rule
import org.apache.spark.sql.classic.Strategy

/**
 * :: Experimental ::
 * Holder for experimental methods for the bravest. We make NO guarantee about the stability
 * regarding binary compatibility and source compatibility of methods here.
 *
 * {{{
 *   spark.experimental.extraStrategies += ...
 * }}}
 *
 * @since 1.3.0
 */
@Experimental
@Unstable
class ExperimentalMethods private[sql]() {

  /**
   * Allows extra strategies to be injected into the query planner at runtime.  Note this API
   * should be considered experimental and is not intended to be stable across releases.
   *
   * @since 1.3.0
   */
  @volatile var extraStrategies: Seq[Strategy] = Nil

  @volatile var extraOptimizations: Seq[Rule[LogicalPlan]] = Nil

  override def clone(): ExperimentalMethods = {
    val result = new ExperimentalMethods
    result.extraStrategies = extraStrategies
    result.extraOptimizations = extraOptimizations
    result
  }
}
