org.datanucleus.store.rdbms.sql.method.SimpleOrderableAggregateMethod Maven / Gradle / Ivy

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Plugin for DataNucleus providing persistence to RDBMS datastores.
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/**********************************************************************
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,
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See the License for the specific language governing permissions and
limitations under the License.

Contributors:
    ...
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package org.datanucleus.store.rdbms.sql.method;

import java.util.List;

import org.datanucleus.ClassLoaderResolver;
import org.datanucleus.exceptions.NucleusException;
import org.datanucleus.query.compiler.CompilationComponent;
import org.datanucleus.store.rdbms.mapping.java.JavaTypeMapping;
import org.datanucleus.store.rdbms.sql.SQLStatement;
import org.datanucleus.store.rdbms.sql.SelectStatement;
import org.datanucleus.store.rdbms.sql.expression.AggregateNumericExpression;
import org.datanucleus.store.rdbms.sql.expression.AggregateStringExpression;
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.SQLExpressionFactory;
import org.datanucleus.store.rdbms.sql.expression.StringExpression;
import org.datanucleus.store.rdbms.sql.expression.StringLiteral;
import org.datanucleus.store.rdbms.sql.expression.StringSubqueryExpression;
import org.datanucleus.store.rdbms.sql.expression.TemporalExpression;
import org.datanucleus.store.rdbms.sql.expression.TemporalSubqueryExpression;
import org.datanucleus.util.Localiser;

/**
 * Expression handler to invoke an SQL aggregated function.
 * 
 * The expression should be null and will return an AggregateXXXExpression
 *     {functionName}({argExpr})
 when processing a result clause
 * If the compilation component is something else then will generate a subquery expression
 * 
 */
public abstract class SimpleOrderableAggregateMethod implements SQLMethod
{
    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(SQLStatement stmt, 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 ||
            stmt.getQueryGenerator().getCompilationComponent() == CompilationComponent.HAVING)
        {
            // FUNC(argExpr)
            // Use same java type as the argument
            SQLExpression argExpr = args.get(0);
            JavaTypeMapping m = argExpr.getJavaTypeMapping();
            if (argExpr instanceof TemporalExpression)
            {
                return new AggregateTemporalExpression(stmt, m, getFunctionName(), args);
            }
            else if (argExpr instanceof StringExpression)
            {
                return new AggregateStringExpression(stmt, m, getFunctionName(), args);
            }
            return new AggregateNumericExpression(stmt, m, getFunctionName(), args);
        }

        // Handle as Subquery "SELECT AVG(expr) FROM tbl"
        SQLExpressionFactory exprFactory = stmt.getSQLExpressionFactory();
        ClassLoaderResolver clr = stmt.getQueryGenerator().getClassLoaderResolver();
        SQLExpression argExpr = args.get(0);
        SelectStatement subStmt = new SelectStatement(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 if (argExpr instanceof StringExpression)
        {
            subqExpr = new StringSubqueryExpression(stmt, subStmt);
        }
        else
        {
            subqExpr = new NumericSubqueryExpression(stmt, subStmt);
        }
        subqExpr.setJavaTypeMapping(subqMapping);
        return subqExpr;
    }
}