com.redhat.lightblue.assoc.QueryPlanIterator Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of lightblue-core-crud Show documentation

There is a newer version: 2.18.0

/*
 Copyright 2013 Red Hat, Inc. and/or its affiliates.

 This file is part of lightblue.

 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with this program.  If not, see .
 */
package com.redhat.lightblue.assoc;

/**
 * Iterates over possible query plans by rearranging the query plan graph.
 *
 * The given query plan is taken as an initial state. Every successive call to
 * next will modify the query plan into a unique tree. Once all
 * possible query plans are iterated, next returns false.
 */
public interface QueryPlanIterator {

    /**
     * Resets the query plan iterator with the given copy of the query plan. The
     * query iterator must assume that this given query plan is in its initial
     * state, and should iterate through different query plans, modifying the
     * given copy.
     */
    void reset(QueryPlan p);

    /**
     * Modifies the query plan into a unique tree.
     *
     * @return If true, tne query plan is configured into a unique tree. If
     * false, query plan is now returned back to its original state during
     * iterator construction, and the iteration is expected to stop.
     */
    public boolean next();
}