cosmos.sql.impl.functions.FieldLimiter.java Source code

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Here is the source code for cosmos.sql.impl.functions.FieldLimiter.java

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/**
 * 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.
 *
 *  Copyright 2013 
 *
 */
package cosmos.sql.impl.functions;

import java.util.List;
import java.util.Map.Entry;

import com.google.common.base.Function;
import com.google.common.base.Predicate;
import com.google.common.collect.Iterables;
import com.google.common.collect.Lists;
import com.google.common.collect.Multimaps;

import cosmos.records.impl.MultimapRecord;
import cosmos.records.values.RecordValue;
import cosmos.results.Column;
import cosmos.sql.call.Field;

/**
 * Function, which limits fields from our returned documents.
 * 
 * 
 */

public class FieldLimiter implements Function<MultimapRecord, MultimapRecord> {

    Predicate<Entry<Column, RecordValue<?>>> limitingPredicate;

    public FieldLimiter(List<Field> fields) {
        limitingPredicate = new FieldLimitPredicate(
                Lists.newArrayList(Iterables.transform(fields, new Function<Field, String>() {
                    @Override
                    public String apply(Field field) {
                        return field.toString();
                    }
                })));

    }

    @Override
    public MultimapRecord apply(MultimapRecord input) {
        return new FieldLimitingQueryResult(input, input.docId(), limitingPredicate);
    }

    private class FieldLimitingQueryResult extends MultimapRecord {
        public FieldLimitingQueryResult(MultimapRecord other, String newDocId,
                Predicate<Entry<Column, RecordValue<?>>> limitingPredicate) {
            super(other, newDocId);
            document = Multimaps.filterEntries(document, limitingPredicate);

        }
    }

    /**
     * Internal predicate that limits portions of a document according to the constructed list of fields
     * 
     * @author phrocker
     * 
     */
    private class FieldLimitPredicate implements Predicate<Entry<Column, RecordValue<?>>> {

        private List<String> fields;

        public FieldLimitPredicate(List<String> fields) {
            this.fields = fields;
        }

        @Override
        public boolean apply(Entry<Column, RecordValue<?>> entry) {
            return fields.contains(entry.getKey().name());
        }
    }

}