FullScanQueryExecutor.java

/*
 * Copyright 2006-2012 Amazon Technologies, Inc. or its affiliates.
 * Amazon, Amazon.com and Carbonado are trademarks or registered trademarks
 * of Amazon Technologies, Inc. or its affiliates.  All rights reserved.
 *
 * 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.amazon.carbonado.qe;

import java.io.IOException;

import com.amazon.carbonado.Cursor;
import com.amazon.carbonado.FetchException;
import com.amazon.carbonado.Query;
import com.amazon.carbonado.Storable;

import com.amazon.carbonado.filter.Filter;
import com.amazon.carbonado.filter.FilterValues;

/**
 * QueryExecutor which fully scans all Storables of a given type.
 *
 * @author Brian S O'Neill
 */
public class FullScanQueryExecutor<S extends Storable> extends AbstractQueryExecutor<S> {
    private final Support<S> mSupport;

    /**
     * @param support support for full scan
     * @throws IllegalArgumentException if support is null
     */
    public FullScanQueryExecutor(Support<S> support) {
        if (support == null && this instanceof Support) {
            support = (Support<S>) this;
        }
        if (support == null) {
            throw new IllegalArgumentException();
        }
        mSupport = support;
    }

    @Override
    public long count(FilterValues<S> values) throws FetchException {
        long count = mSupport.countAll();
        if (count == -1) {
            count = super.count(values);
        }
        return count;
    }

    @Override
    public long count(FilterValues<S> values, Query.Controller controller) throws FetchException {
        long count = mSupport.countAll(controller);
        if (count == -1) {
            count = super.count(values, controller);
        }
        return count;
    }

    /**
     * Returns an open filter.
     */
    public Filter<S> getFilter() {
        return Filter.getOpenFilter(mSupport.getStorableType());
    }

    public Cursor<S> fetch(FilterValues<S> values) throws FetchException {
        return mSupport.fetchAll();
    }

    public Cursor<S> fetch(FilterValues<S> values, Query.Controller controller)
        throws FetchException
    {
        return mSupport.fetchAll(controller);
    }

    /**
     * Returns an empty list.
     */
    public OrderingList<S> getOrdering() {
        return OrderingList.emptyList();
    }

    public boolean printPlan(Appendable app, int indentLevel, FilterValues<S> values)
        throws IOException
    {
        indent(app, indentLevel);
        app.append("full scan: ");
        app.append(mSupport.getStorableType().getName());
        newline(app);
        return true;
    }

    /**
     * Provides support for {@link FullScanQueryExecutor}.
     */
    public static interface Support<S extends Storable> {
        Class<S> getStorableType();

        /**
         * Counts all Storables. Implementation may return -1 to indicate that
         * default count algorithm should be used.
         */
        long countAll() throws FetchException;

        /**
         * Counts all Storables. Implementation may return -1 to indicate that
         * default count algorithm should be used.
         *
         * @param controller optional controller which can abort query operation
         */
        long countAll(Query.Controller controller) throws FetchException;

        /**
         * Perform a full scan of all Storables.
         */
        Cursor<S> fetchAll() throws FetchException;

        /**
         * Perform a full scan of all Storables.
         *
         * @param controller optional controller which can abort query operation
         */
        Cursor<S> fetchAll(Query.Controller controller) throws FetchException;
    }
}