SelectOperation.java

/**
 * 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.
 */
package io.horizondb.db.operations;

import io.horizondb.db.HorizonDBException;
import io.horizondb.db.Operation;
import io.horizondb.db.OperationContext;
import io.horizondb.db.databases.Database;
import io.horizondb.db.series.TimeSeries;
import io.horizondb.model.core.Predicate;
import io.horizondb.model.core.Projection;
import io.horizondb.model.core.Record;
import io.horizondb.model.core.ResourceIterator;
import io.horizondb.model.protocol.Msg;
import io.horizondb.model.protocol.Msgs;
import io.horizondb.model.protocol.SelectPayload;

import java.io.IOException;

/**
 * <code>Operation</code> used to select data.
 */
final class SelectOperation implements Operation {

    /**
     * {@inheritDoc}
     */
    @Override
    public Object perform(OperationContext context, Msg<?> request) throws IOException, HorizonDBException {

        SelectPayload payload = Msgs.getPayload(request);

        Database database = context.getDatabaseManager().getDatabase(payload.getDatabaseName());

        TimeSeries series = database.getTimeSeries(payload.getSeriesName());
        
        Projection projection = payload.getProjection();
        Predicate predicate = payload.getPredicate();
        try (ResourceIterator<? extends Record> iterator = series.read(projection, predicate)) {
            return new ChunkedRecordSet(request.getHeader(),
                                        projection.getDefinition(series.getDefinition()),
                                        new ChunkedRecordStream(request.getHeader(), iterator));
        }
    }
}