vxquery-core/src/main/java/org/apache/vxquery/runtime/functions/aggregate/AbstractMaxMinAggregateEvaluatorFactory.java

/*
 * 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.
 */
package org.apache.vxquery.runtime.functions.aggregate;

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

import org.apache.hyracks.algebricks.runtime.base.IAggregateEvaluator;
import org.apache.hyracks.algebricks.runtime.base.IScalarEvaluator;
import org.apache.hyracks.algebricks.runtime.base.IScalarEvaluatorFactory;
import org.apache.hyracks.api.exceptions.HyracksDataException;
import org.apache.hyracks.data.std.api.IPointable;
import org.apache.hyracks.data.std.util.ArrayBackedValueStorage;
import org.apache.vxquery.datamodel.accessors.SequencePointable;
import org.apache.vxquery.datamodel.accessors.TaggedValuePointable;
import org.apache.vxquery.datamodel.accessors.TypedPointables;
import org.apache.vxquery.datamodel.values.ValueTag;
import org.apache.vxquery.datamodel.values.XDMConstants;
import org.apache.vxquery.exceptions.ErrorCode;
import org.apache.vxquery.exceptions.SystemException;
import org.apache.vxquery.runtime.functions.base.AbstractTaggedValueArgumentAggregateEvaluator;
import org.apache.vxquery.runtime.functions.base.AbstractTaggedValueArgumentAggregateEvaluatorFactory;
import org.apache.vxquery.runtime.functions.comparison.AbstractValueComparisonOperation;
import org.apache.vxquery.runtime.functions.util.FunctionHelper;

public abstract class AbstractMaxMinAggregateEvaluatorFactory extends
        AbstractTaggedValueArgumentAggregateEvaluatorFactory {
    private static final long serialVersionUID = 1L;

    public AbstractMaxMinAggregateEvaluatorFactory(IScalarEvaluatorFactory[] args) {
        super(args);
    }

    @Override
    protected IAggregateEvaluator createEvaluator(IScalarEvaluator[] args) throws HyracksDataException {
        final AbstractValueComparisonOperation aOpComparison = createValueComparisonOperation();
        final TaggedValuePointable tvp2 = (TaggedValuePointable) TaggedValuePointable.FACTORY.createPointable();
        final SequencePointable seqp = (SequencePointable) SequencePointable.FACTORY.createPointable();
        final TypedPointables tp1 = new TypedPointables();
        final TypedPointables tp2 = new TypedPointables();

        final ArrayBackedValueStorage abvs = new ArrayBackedValueStorage();
        final DataOutput dOut = abvs.getDataOutput();

        return new AbstractTaggedValueArgumentAggregateEvaluator(args) {
            long count;

            @Override
            public void init() {
                count = 0;
            }

            @Override
            public void finishPartial(IPointable result) {
                finish(result);
            }

            @Override
            public void finish(IPointable result) {
                if (count == 0) {
                    XDMConstants.setEmptySequence(result);
                } else {
                    result.set(abvs);
                }
            }

            @Override
            protected void step(TaggedValuePointable[] args) throws HyracksDataException {
                TaggedValuePointable tvp1 = args[0];
                if (tvp1.getTag() == ValueTag.SEQUENCE_TAG) {
                    // The local aggregate did not find a value so the global aggregate is receiving a empty sequence.
                    tvp1.getValue(seqp);
                    int seqLen = seqp.getEntryCount();
                    if (seqLen != 0) {
                        throw new SystemException(ErrorCode.FORG0006);
                    }
                } else {
                    if (count != 0) {
                        tvp2.set(abvs.getByteArray(), abvs.getStartOffset(), abvs.getLength());
                    }
                    if (count == 0
                            || FunctionHelper.transformThenCompareMinMaxTaggedValues(aOpComparison, tvp1, tvp2, dCtx,
                                    tp1, tp2)) {
                        try {
                            abvs.reset();
                            dOut.write(tvp1.getByteArray(), tvp1.getStartOffset(), tvp1.getLength());
                        } catch (IOException e) {
                            throw new SystemException(ErrorCode.SYSE0001, e);
                        }
                    }
                    count++;
                }
            }

        };
    }

    protected abstract AbstractValueComparisonOperation createValueComparisonOperation();
}