com.google.gerrit.server.index.PredicateWrapper.java Source code

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Here is the source code for com.google.gerrit.server.index.PredicateWrapper.java

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// Copyright (C) 2013 The Android Open Source Project
//
// 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 com.google.gerrit.server.git;

package com.google.gerrit.server.index;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;
import com.google.common.collect.Lists;
import com.google.gerrit.server.query.Predicate;
import com.google.gerrit.server.query.QueryParseException;
import com.google.gerrit.server.query.change.ChangeData;
import com.google.gerrit.server.query.change.ChangeDataSource;
import com.google.gwtorm.server.OrmException;
import com.google.gwtorm.server.ResultSet;

import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;

/**
 * Wrapper combining an {@link IndexPredicate} together with a
 * {@link ChangeDataSource} that returns matching results from the index.
 * <p>
 * Appropriate to return as the rootmost predicate that can be processed using
 * the secondary index; such predicates must also implement
 * {@link ChangeDataSource} to be chosen by the query processor.
 */
public class PredicateWrapper extends Predicate<ChangeData> implements ChangeDataSource {
    private final Predicate<ChangeData> pred;
    private final List<ChangeDataSource> sources;

    public PredicateWrapper(Predicate<ChangeData> pred, ChangeIndex index) throws QueryParseException {
        this(pred, ImmutableList.of(index));
    }

    public PredicateWrapper(Predicate<ChangeData> pred, Collection<ChangeIndex> indexes)
            throws QueryParseException {
        this.pred = pred;
        sources = Lists.newArrayListWithCapacity(indexes.size());
        for (ChangeIndex index : indexes) {
            sources.add(index.getSource(pred));
        }
    }

    @Override
    public int getCardinality() {
        int n = 0;
        for (ChangeDataSource source : sources) {
            n += source.getCardinality();
        }
        return n;
    }

    @Override
    public boolean hasChange() {
        for (ChangeDataSource source : sources) {
            if (!source.hasChange()) {
                return false;
            }
        }
        return true;
    }

    @Override
    public ResultSet<ChangeData> read() throws OrmException {
        final List<ResultSet<ChangeData>> results = Lists.newArrayListWithCapacity(sources.size());
        for (ChangeDataSource source : sources) {
            results.add(source.read());
        }
        return new ResultSet<ChangeData>() {
            @Override
            public Iterator<ChangeData> iterator() {
                // TODO(dborowitz): May return duplicates since moving a document
                // between indexes is not atomic.
                return Iterables.concat(results).iterator();
            }

            @Override
            public List<ChangeData> toList() {
                return Collections.unmodifiableList(Lists.newArrayList(iterator()));
            }

            @Override
            public void close() {
                for (ResultSet<ChangeData> rs : results) {
                    rs.close();
                }
            }
        };
    }

    @Override
    public Predicate<ChangeData> copy(Collection<? extends Predicate<ChangeData>> children) {
        return this;
    }

    @Override
    public boolean match(ChangeData cd) throws OrmException {
        return pred.match(cd);
    }

    @Override
    public int getCost() {
        return pred.getCost();
    }

    @Override
    public int hashCode() {
        return pred.hashCode();
    }

    @Override
    public boolean equals(Object other) {
        return other != null && getClass() == other.getClass() && pred.equals(((PredicateWrapper) other).pred);
    }

    @Override
    public String toString() {
        return "index(" + pred + ")";
    }
}