| /* |
| * 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.cassandra.cql3.functions; |
| |
| import java.nio.ByteBuffer; |
| import java.util.List; |
| |
| import org.apache.cassandra.exceptions.InvalidRequestException; |
| |
| /** |
| * Performs a calculation on a set of values and return a single value. |
| */ |
| public interface AggregateFunction extends Function |
| { |
| /** |
| * Creates a new <code>Aggregate</code> instance. |
| * |
| * @return a new <code>Aggregate</code> instance. |
| */ |
| public Aggregate newAggregate() throws InvalidRequestException; |
| |
| /** |
| * An aggregation operation. |
| */ |
| interface Aggregate |
| { |
| /** |
| * Adds the specified input to this aggregate. |
| * |
| * @param protocolVersion native protocol version |
| * @param values the values to add to the aggregate. |
| */ |
| public void addInput(int protocolVersion, List<ByteBuffer> values) throws InvalidRequestException; |
| |
| /** |
| * Computes and returns the aggregate current value. |
| * |
| * @param protocolVersion native protocol version |
| * @return the aggregate current value. |
| */ |
| public ByteBuffer compute(int protocolVersion) throws InvalidRequestException; |
| |
| /** |
| * Reset this aggregate. |
| */ |
| public void reset(); |
| } |
| } |