/*
 * Copyright Red Hat, Inc. and/or its affiliates
 * and other contributors as indicated by the @author tags and
 * the COPYRIGHT.txt file distributed with this work.
 *
 * Licensed 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.teiid;

/**
 * Interface to be implemented by a user defined aggregate function.
 * @param <T>
 */
public interface UserDefinedAggregate<T> {
    /**
     * Called when state from the current partition can be forgotten
     */
    void reset();
    /**
     * Called to get the current value.  May be called multiple times in the same
     * partition for windowed aggregates.
     * @param commandContext
     * @return
     */
    T getResult(CommandContext commandContext);

}
