/*
 * 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.flink.table.runtime.functions;

import org.apache.flink.table.dataformat.BaseRow;

/**
 * Basic interface for handling aggregate function.
 */
public interface AggHandleFunctionBase {
	/**
	 * Initialization method for the function. It is called before the actual working methods.
	 */
	void open(ExecutionContext ctx) throws Exception;

	/**
	 * Merges the other accumulators into current accumulators.
	 *
	 * @param accumulators The other row of accumulators
	 */
	void merge(BaseRow accumulators) throws Exception;

	/**
	 * Set the current accumulators (saved in a row) which contains the current.
	 * aggregated results
	 * @param accumulators current accumulators
	 */
	void setAccumulators(BaseRow accumulators) throws Exception;

	/**
	 * Resets all the accumulators.
	 */
	void resetAccumulators() throws Exception;

	/**
	 * Gets the current accumulators (saved in a row) which contains the current
	 * aggregated results.
	 * @return the current accumulators
	 */
	BaseRow getAccumulators() throws Exception;

	/**
	 * Initializes the accumulators and save them to a accumulators row.
	 *
	 * @return a row of accumulators which contains the aggregated results
	 */
	BaseRow createAccumulators() throws Exception;

	/**
	 * Cleanup for the retired accumulators state.
	 */
	void cleanup() throws Exception;

	/**
	 * Tear-down method for this function. It can be used for clean up work.
	 * By default, this method does nothing.
	 */
	void close() throws Exception;
}