asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/aggregates/std/CountAggregateFunction.java

package edu.uci.ics.asterix.runtime.aggregates.std;

import java.io.DataOutput;
import java.io.IOException;

import edu.uci.ics.asterix.formats.nontagged.AqlSerializerDeserializerProvider;
import edu.uci.ics.asterix.om.base.AInt32;
import edu.uci.ics.asterix.om.base.AMutableInt32;
import edu.uci.ics.asterix.om.base.ANull;
import edu.uci.ics.asterix.om.types.ATypeTag;
import edu.uci.ics.asterix.om.types.BuiltinType;
import edu.uci.ics.asterix.om.types.EnumDeserializer;
import edu.uci.ics.hyracks.algebricks.common.exceptions.AlgebricksException;
import edu.uci.ics.hyracks.algebricks.runtime.base.ICopyAggregateFunction;
import edu.uci.ics.hyracks.algebricks.runtime.base.ICopyEvaluator;
import edu.uci.ics.hyracks.algebricks.runtime.base.ICopyEvaluatorFactory;
import edu.uci.ics.hyracks.api.dataflow.value.ISerializerDeserializer;
import edu.uci.ics.hyracks.data.std.api.IDataOutputProvider;
import edu.uci.ics.hyracks.data.std.util.ArrayBackedValueStorage;
import edu.uci.ics.hyracks.dataflow.common.data.accessors.IFrameTupleReference;

/**
 * count(NULL) returns NULL.
 */
public class CountAggregateFunction implements ICopyAggregateFunction {
    private AMutableInt32 result = new AMutableInt32(-1);
    @SuppressWarnings("unchecked")
    private ISerializerDeserializer<AInt32> int32Serde = AqlSerializerDeserializerProvider.INSTANCE
            .getSerializerDeserializer(BuiltinType.AINT32);
    @SuppressWarnings("unchecked")
    private ISerializerDeserializer<ANull> nullSerde = AqlSerializerDeserializerProvider.INSTANCE
            .getSerializerDeserializer(BuiltinType.ANULL);
    private ArrayBackedValueStorage inputVal = new ArrayBackedValueStorage();
    private ICopyEvaluator eval;
    private boolean metNull;
    private int cnt;
    private DataOutput out;

    public CountAggregateFunction(ICopyEvaluatorFactory[] args, IDataOutputProvider output) throws AlgebricksException {
        eval = args[0].createEvaluator(inputVal);
        out = output.getDataOutput();
    }

    @Override
    public void init() {
        cnt = 0;
        metNull = false;
    }

    @Override
    public void step(IFrameTupleReference tuple) throws AlgebricksException {
        inputVal.reset();
        eval.evaluate(tuple);
        ATypeTag typeTag = EnumDeserializer.ATYPETAGDESERIALIZER.deserialize(inputVal.getByteArray()[0]);
        // Ignore SYSTEM_NULL.
        if (typeTag == ATypeTag.NULL) {
            metNull = true;
        } else {
            cnt++;
        }
    }

    @Override
    public void finish() throws AlgebricksException {
        try {
            if (metNull) {
                nullSerde.serialize(ANull.NULL, out);
            } else {
                result.setValue(cnt);
                int32Serde.serialize(result, out);
            }
        } catch (IOException e) {
            throw new AlgebricksException(e);
        }
    }

    @Override
    public void finishPartial() throws AlgebricksException {
        finish();
    }
}