/**
 * 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.hadoop.hive.ql.optimizer;

import org.apache.hadoop.hive.ql.log.PerfLogger;
import org.apache.hadoop.hive.ql.parse.ParseContext;
import org.apache.hadoop.hive.ql.parse.SemanticException;
import org.apache.hadoop.hive.ql.session.SessionState;

/**
 * Optimizer interface. All the rule-based optimizations implement this
 * interface. All the transformations are invoked sequentially. They take the
 * current parse context (which contains the operator tree among other things),
 * perform all the optimizations, and then return the updated parse context.
 */
public abstract class Transform {
  /**
   * All transformation steps implement this interface.
   * 
   * @param pctx
   *          input parse context
   * @return ParseContext
   * @throws SemanticException
   */
  public abstract ParseContext transform(ParseContext pctx) throws SemanticException;
  
  public void beginPerfLogging() {
    PerfLogger perfLogger = SessionState.getPerfLogger();
    perfLogger.PerfLogBegin(this.getClass().getName(), PerfLogger.OPTIMIZER);
  }

  public void endPerfLogging() {
    PerfLogger perfLogger = SessionState.getPerfLogger();
    perfLogger.PerfLogEnd(this.getClass().getName(), PerfLogger.OPTIMIZER);
  }
  public void endPerfLogging(String additionalInfo) {
    PerfLogger perfLogger = SessionState.getPerfLogger();
	perfLogger.PerfLogEnd(this.getClass().getName(), PerfLogger.OPTIMIZER, additionalInfo);
  }  
}