| gvSIG desktop 1

package com.hardcode.gdbms.engine.strategies;

import com.hardcode.gdbms.driver.exceptions.ReadDriverException;

import com.hardcode.gdbms.engine.customQuery.CustomQuery;

import com.hardcode.gdbms.engine.customQuery.QueryException;

import com.hardcode.gdbms.engine.data.DataSource;

import com.hardcode.gdbms.engine.instruction.Adapter;

import com.hardcode.gdbms.engine.instruction.Expression;

import com.hardcode.gdbms.engine.instruction.Utilities;

import com.hardcode.gdbms.engine.values.NumericValue;

import com.hardcode.gdbms.engine.values.Value;

/**

 * @author Fernando Gonz?lez Cort?s

 */

public class SumQuery implements CustomQuery{

        /**

         * @throws QueryException

         * @see com.hardcode.gdbms.engine.customQuery.CustomQuery#evaluate(com.hardcode.gdbms.engine.data.DataSource[], com.hardcode.gdbms.engine.instruction.Expression[])

         */

        public OperationDataSource evaluate(DataSource[] tables, Expression[] values) throws QueryException {

                if (tables.length != 1) throw new QueryException("SUM only operates on one table");

                if (values.length != 1) throw new QueryException("SUM only operates with one value");

                ((Adapter) values[0]).getInstructionContext().setFromTables(new DataSource[]{tables[0]});

                ((Adapter) values[0]).getInstructionContext().setDs(tables[0]);

                String fieldName = values[0].getFieldName();

                if (fieldName == null) throw new QueryException("field not found " + Utilities.getText(((Adapter)values[0]).getEntity()));

                double res = 0;

                try {

                        tables[0].start();

                        int fieldIndex = tables[0].getFieldIndexByName(fieldName);

                        if (fieldIndex == -1) throw new RuntimeException("we found the field name of the expression but could not find the field index?");

                        for (int i = 0; i < tables[0].getRowCount(); i++) {

                                Value v = tables[0].getFieldValue(i, fieldIndex);

                                if (v instanceof NumericValue){

                                        res += ((NumericValue) v).doubleValue();

                                }else{

                                        throw new QueryException("SUM only operates with numeric fields");

                                }

                        }

                        tables[0].stop();

                } catch (ReadDriverException e) {

                        throw new QueryException("Error reading data", e);

                }

                return new SumDataSource(res);

        }

    /**

     * @see com.hardcode.gdbms.engine.customQuery.CustomQuery#getName()

     */

    public String getName() {

        return "SUMQUERY";

    }

}