org.hibernate.dialect.function.AvgWithArgumentCastFunction Maven / Gradle / Ivy
/*
* Hibernate, Relational Persistence for Idiomatic Java
*
* Copyright (c) 2010, Red Hat Inc. or third-party contributors as
* indicated by the @author tags or express copyright attribution
* statements applied by the authors. All third-party contributions are
* distributed under license by Red Hat Inc.
*
* This copyrighted material is made available to anyone wishing to use, modify,
* copy, or redistribute it subject to the terms and conditions of the GNU
* Lesser General Public License, as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this distribution; if not, write to:
* Free Software Foundation, Inc.
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*/
package org.hibernate.dialect.function;
import java.util.List;
import org.hibernate.QueryException;
import org.hibernate.engine.SessionFactoryImplementor;
/**
* Some databases strictly return the type of the of the aggregation value for AVG which is
* problematic in the case of averaging integers because the decimals will be dropped. The usual workaround
* is to cast the integer argument as some form of double/decimal.
*
* A downside to this approach is that we always wrap the avg() argument in a cast even though we may not need or want
* to. A more full-featured solution would be defining {@link SQLFunction} such that we render based on the first
* argument; essentially have {@link SQLFunction} describe the basic metadata about the function and merge the
* {@link SQLFunction#getReturnType} and {@link SQLFunction#render} methods into a
*
* @author Steve Ebersole
*/
public class AvgWithArgumentCastFunction extends AvgFunction {
private final TemplateRenderer renderer;
public AvgWithArgumentCastFunction(String castType) {
renderer = new TemplateRenderer( "avg(cast(?1 as " + castType + "))" );
}
public String render(List args, SessionFactoryImplementor factory) throws QueryException {
return renderer.render( args, factory );
}
}