/**********************************************************************
Copyright (c) 2008 Andy Jefferson and others. All rights reserved.
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.
Contributors:
...
**********************************************************************/
package org.datanucleus.store.rdbms.sql.method;
import java.util.List;
import org.datanucleus.exceptions.NucleusException;
import org.datanucleus.query.compiler.CompilationComponent;
import org.datanucleus.store.mapped.mapping.JavaTypeMapping;
import org.datanucleus.store.rdbms.sql.SQLStatement;
import org.datanucleus.store.rdbms.sql.expression.AggregateNumericExpression;
import org.datanucleus.store.rdbms.sql.expression.AggregateTemporalExpression;
import org.datanucleus.store.rdbms.sql.expression.NumericSubqueryExpression;
import org.datanucleus.store.rdbms.sql.expression.SQLExpression;
import org.datanucleus.store.rdbms.sql.expression.StringLiteral;
import org.datanucleus.store.rdbms.sql.expression.TemporalExpression;
import org.datanucleus.store.rdbms.sql.expression.TemporalSubqueryExpression;
/**
* Expression handler to invoke an SQL aggregated function.
* <ul>
* <li>The expression should be null and will return an AggregateXXXExpression
* <pre>{functionName}({argExpr})</pre> when processing a result clause</li>
* <li>If the compilation component is something else then will generate a subquery expression</li>
* </ul>
*/
public abstract class SimpleOrderableAggregateMethod extends AbstractSQLMethod
{
protected abstract String getFunctionName();
/* (non-Javadoc)
* @see org.datanucleus.store.rdbms.sql.method.SQLMethod#getExpression(org.datanucleus.store.rdbms.sql.expression.SQLExpression, java.util.List)
*/
public SQLExpression getExpression(SQLExpression expr, List args)
{
if (expr != null)
{
throw new NucleusException(LOCALISER.msg("060002", getFunctionName(), expr));
}
else if (args == null || args.size() != 1)
{
throw new NucleusException(getFunctionName() + " is only supported with a single argument");
}
if (stmt.getQueryGenerator().getCompilationComponent() == CompilationComponent.RESULT)
{
// FUNC(argExpr)
JavaTypeMapping m = null;
if (args.get(0) instanceof SQLExpression)
{
// Use same java type as the argument
SQLExpression argExpr = (SQLExpression)args.get(0);
m = getMappingForClass(argExpr.getJavaTypeMapping().getJavaType());
if (args.get(0) instanceof TemporalExpression)
{
return new AggregateTemporalExpression(stmt, m, getFunctionName(), args);
}
else
{
return new AggregateNumericExpression(stmt, m, getFunctionName(), args);
}
}
else
{
// What is coming through here?
// Fallback to the type for this aggregate TODO Allow for temporal types
m = getMappingForClass(double.class);
return new AggregateNumericExpression(stmt, m, getFunctionName(), args);
}
}
else
{
// Handle as Subquery "SELECT AVG(expr) FROM tbl"
SQLExpression argExpr = (SQLExpression)args.get(0);
SQLStatement subStmt = new SQLStatement(stmt, stmt.getRDBMSManager(),
argExpr.getSQLTable().getTable(), argExpr.getSQLTable().getAlias(), null);
subStmt.setClassLoaderResolver(clr);
JavaTypeMapping mapping =
stmt.getRDBMSManager().getMappingManager().getMappingWithDatastoreMapping(String.class, false, false, clr);
String aggregateString = getFunctionName() + "(" + argExpr.toSQLText() + ")";
SQLExpression aggExpr = exprFactory.newLiteral(subStmt, mapping, aggregateString);
((StringLiteral)aggExpr).generateStatementWithoutQuotes();
subStmt.select(aggExpr, null);
JavaTypeMapping subqMapping = exprFactory.getMappingForType(Integer.class, false);
SQLExpression subqExpr = null;
if (argExpr instanceof TemporalExpression)
{
subqExpr = new TemporalSubqueryExpression(stmt, subStmt);
}
else
{
subqExpr = new NumericSubqueryExpression(stmt, subStmt);
}
subqExpr.setJavaTypeMapping(subqMapping);
return subqExpr;
}
}
}