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package org.apache.torque.util;

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */

/**
 * This is a utility class which eases counting of Datasets
 *
 * @author <a href="mailto:Martin.Goulet@sungard.com">Martin Goulet</a>
 * @author <a href="mailto:eric.lambert@sungard.com">Eric Lambert</a>
 * @author <a href="mailto:sebastien.paquette@sungard.com">Sebastien Paquette</a>
 * @author <a href="mailto:fischer@seitenbau.de">Thomas Fischer</a>
 * @version $Id: CountHelper.java 473821 2006-11-11 22:37:25Z tv $
 */
import java.sql.Connection;
import java.util.List;

import org.apache.torque.TorqueException;

import com.workingdogs.village.DataSetException;
import com.workingdogs.village.Record;

public class CountHelper
{
    /**
     * The COUNT function returns the number of rows in a query.
     * Does not use a connection, hardcode the column to "*" and
     * set the distinct qualifier to false.
     * Only use this function if you have added additional constraints to
     * the criteria, otherwise Torque does not know which table it should
     * count the datasets in.
     *
     * @param c Criteria to get the count for.
     * @return number of rows matching the query provided
     * @throws TorqueException if the query could not be executed
     */
    public int count(Criteria c) throws TorqueException
    {
        return count(c, null, "*");
    }

    /**
     * The COUNT function returns the number of rows in a query.
     * Hard code the distinct parameter to false and set the column to "*".
     * Only use this function if you have added additional constraints to
     * the criteria, otherwise Torque does not know which table it should
     * count the datasets in.
     *
     * @param c Criteria to get the count for.
     * @param conn Connection to use
     * @return number of rows matching the query provided
     * @throws TorqueException if the query could not be executed
     */
    public int count(Criteria c, Connection conn) throws TorqueException
    {
        return count(c, conn, "*");
    }

    /**
     * Returns the number of rows in a query.
     *
     * @param c Criteria to get the count for.
     * @param columnName Name of database Column which is counted. Preferably,
     *        use the primary key here.
     * @return number of rows matching the query provided
     * @throws TorqueException if the query could not be executed
     */
    public int count(Criteria c, String columnName)
        throws TorqueException
    {
        return count(c, null, columnName);
    }

    /**
     * Returns the number of rows in a query.
     *
     * @param c Criteria to get the count for.
     * @param conn Connection to use
     * @param columnName Name of database Column which is counted. Preferably,
     *        use the primary key here.
     * @return number of rows matching the query provided
     * @throws TorqueException if the query could not be executed
     */
    public int count(Criteria c, Connection conn, String columnName)
        throws TorqueException
    {
        /* Clear the select columns. */
        c.getSelectColumns().clear();
        c.getOrderByColumns().clear();
        c.getGroupByColumns().clear();

        UniqueList criteriaSelectModifiers;
        criteriaSelectModifiers = c.getSelectModifiers();

        boolean distinct = false;
        if (criteriaSelectModifiers != null
            && criteriaSelectModifiers.size() > 0
            && criteriaSelectModifiers.contains(SqlEnum.DISTINCT.toString()))
        {
            criteriaSelectModifiers.remove(SqlEnum.DISTINCT.toString());
            distinct = true;
        }

        StringBuffer countStr = new StringBuffer("COUNT(");
        countStr.append(distinct ? SqlEnum.DISTINCT.toString() : "");
        countStr.append(columnName);
        countStr.append(")");

        c.addSelectColumn(countStr.toString());

        List result;
        if (conn == null)
        {
            result = BasePeer.doSelect(c);
        }
        else
        {
            result = BasePeer.doSelect(c, conn);
        }

        Record record = (Record) result.get(0);
        try
        {
            return record.getValue(1).asInt();
        }
        catch (DataSetException e)
        {
            throw new TorqueException(e);
        }
    }
}
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