org.h2.api.AggregateFunction Maven / Gradle / Ivy
/*
* Copyright 2004-2011 H2 Group. Multiple-Licensed under the H2 License,
* Version 1.0, and under the Eclipse Public License, Version 1.0
* (http://h2database.com/html/license.html).
* Initial Developer: H2 Group
*/
package org.h2.api;
import java.sql.Connection;
import java.sql.SQLException;
/**
* A user-defined aggregate function needs to implement this interface.
* The class must be public and must have a public non-argument constructor.
*/
public interface AggregateFunction {
/**
* This method is called when the aggregate function is used.
* A new object is created for each invocation.
*
* @param conn a connection to the database
*/
void init(Connection conn) throws SQLException;
/**
* This method must return the SQL type of the method, given the SQL type of
* the input data. The method should check here if the number of parameters
* passed is correct, and if not it should throw an exception.
*
* @param inputTypes the SQL type of the parameters
* @return the SQL type of the result
*/
int getType(int[] inputTypes) throws SQLException;
/**
* This method is called once for each row.
* If the aggregate function is called with multiple parameters,
* those are passed as array.
*
* @param value the value(s) for this row
*/
void add(Object value) throws SQLException;
/**
* This method returns the computed aggregate value.
*
* @return the aggregated value
*/
Object getResult() throws SQLException;
}