extras/indexing/src/main/java/org/apache/rya/indexing/external/matching/OptionalJoinSegment.java

package org.apache.rya.indexing.external.matching;
/*
 * 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.
 */

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.apache.rya.indexing.external.tupleSet.ExternalTupleSet;
import org.apache.rya.rdftriplestore.inference.DoNotExpandSP;
import org.apache.rya.rdftriplestore.utils.FixedStatementPattern;
import org.eclipse.rdf4j.query.algebra.Filter;
import org.eclipse.rdf4j.query.algebra.Join;
import org.eclipse.rdf4j.query.algebra.LeftJoin;
import org.eclipse.rdf4j.query.algebra.QueryModelNode;
import org.eclipse.rdf4j.query.algebra.TupleExpr;
import org.eclipse.rdf4j.query.algebra.ValueExpr;
import org.eclipse.rdf4j.query.algebra.evaluation.impl.ExternalSet;

import com.google.common.base.Preconditions;
import com.google.common.collect.Sets;

/**
 * An OptionalJoinSegment represents the portion of a {@link TupleExpr} that is
 * connected by Filters, LeftJoins, and Joins. All nodes in the portion of the
 * TupleExpr that are connected via these node types are gathered into an
 * ordered and an unordered list that can easily be compared with
 * {@link ExternalTupleSet} nodes for sub-query matching to use with Precomputed
 * Joins.
 *
 */
public class OptionalJoinSegment<T extends ExternalSet> extends AbstractQuerySegment<T> {

    public OptionalJoinSegment(Join join) {
        Preconditions.checkNotNull(join);
        createJoinSegment(join);
    }

    public OptionalJoinSegment(LeftJoin join) {
        Preconditions.checkNotNull(join);
        createJoinSegment(join);
    }

    public OptionalJoinSegment(Filter filter) {
        Preconditions.checkNotNull(filter);
        createJoinSegment(filter);
    }
    
    public OptionalJoinSegment(Set<QueryModelNode> unorderedNodes, List<QueryModelNode> orderedNodes, Map<ValueExpr, Filter> filterMap) {
        this.unorderedNodes = unorderedNodes;
        this.orderedNodes = orderedNodes;
        this.conditionMap = filterMap;
    }

    private void createJoinSegment(TupleExpr te) {
        orderedNodes = getJoinArgs(te, orderedNodes);
        unorderedNodes = Sets.newHashSet(orderedNodes);
    }

    /**
     * This method matches the ordered nodes returned by
     * {@link OptionalJoinSegment #getOrderedNodes()} for nodeToReplace with a subset of
     * the ordered nodes for this OptionalJoinSegment. The order of the nodes for
     * nodeToReplace must match the order of the nodes as a subset of
     * orderedNodes
     *
     * @param segment
     *            - nodes to be replaced by ExternalSet node
     * @param set
     *            - ExternalSet node that will replace specified query nodes
     */
    @Override
    public boolean replaceWithExternalSet(QuerySegment<T> segment, T set) {
        Preconditions.checkNotNull(segment != null);
        Preconditions.checkNotNull(set);
        if (!containsQuerySegment(segment)) {
            return false;
        }
        List<QueryModelNode> nodeList = segment.getOrderedNodes();
        int begin = orderedNodes.indexOf(nodeList.get(0));
        // TODO this assumes no duplicate nodes
        if (begin < 0 || begin + nodeList.size() > orderedNodes.size()
                || !nodeList.equals(orderedNodes.subList(begin, begin + nodeList.size()))) {
            return false;
        }
        orderedNodes.removeAll(nodeList);
        orderedNodes.add(begin, set);
        unorderedNodes.removeAll(nodeList);
        unorderedNodes.add(set);
        for (QueryModelNode q : nodeList) {
            if (q instanceof ValueExpr) {
                conditionMap.remove(q);
            }
        }
        return true;
    }

    /**
     *
     * @param tupleExpr
     *            - the query object that will be traversed by this method
     * @param joinArgs
     *            - all nodes connected by Joins, LeftJoins, and Filters
     * @return - List containing all nodes connected by Joins, LeftJoins, and
     *         Filters. This List contains the {@link ValueExpr} in place of the
     *         Filter and a {@link FlattenedOptional} in place of the LeftJoin
     *         for ease of comparison with PCJ nodes.
     */
    private List<QueryModelNode> getJoinArgs(TupleExpr tupleExpr, List<QueryModelNode> joinArgs) {

        if (tupleExpr instanceof Join) {
            if (!(((Join) tupleExpr).getLeftArg() instanceof FixedStatementPattern)
                    && !(((Join) tupleExpr).getRightArg() instanceof DoNotExpandSP)) {
                Join join = (Join) tupleExpr;
                getJoinArgs(join.getRightArg(), joinArgs);
                getJoinArgs(join.getLeftArg(), joinArgs);
            }
        } else if (tupleExpr instanceof LeftJoin) {
            LeftJoin lj = (LeftJoin) tupleExpr;
            joinArgs.add(new FlattenedOptional(lj));
            getJoinArgs(lj.getLeftArg(), joinArgs);
        } else if (tupleExpr instanceof Filter) {
            Filter filter = (Filter) tupleExpr;
            joinArgs.add(filter.getCondition());
            conditionMap.put(filter.getCondition(), filter);
            getJoinArgs(filter.getArg(), joinArgs);
        } else {
            joinArgs.add(tupleExpr);
        }
        return joinArgs;
    }
    
    
    @Override
    public OptionalJoinSegment<T> clone() {
        List<QueryModelNode> order  = new ArrayList<>();
        for(QueryModelNode node: orderedNodes) {
            order.add(node.clone());
        }
        
        Set<QueryModelNode> unorder = Sets.newHashSet(order);
        
        Map<ValueExpr, Filter> map = new HashMap<>();
        for(ValueExpr expr: conditionMap.keySet()) {
            map.put(expr.clone(), conditionMap.get(expr).clone());
        }
        return new OptionalJoinSegment<T>(unorder, order, map);
    }

}