cosmos.impl.DedupingPredicate.java Source code

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Here is the source code for cosmos.impl.DedupingPredicate.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 Josh Elser
 *
 */
package cosmos.impl;

import java.nio.charset.CharacterCodingException;
import java.util.Map.Entry;
import java.util.Set;

import org.apache.accumulo.core.data.Key;
import org.apache.accumulo.core.data.Value;
import org.apache.hadoop.io.Text;

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

import cosmos.options.Defaults;

/**
 * This is apt to be stupidly slow. Perhaps use a bloomfilter instead?
 * Perhaps the API itself should just allow the client to specify when it
 * cares about getting dupes.
 */
public class DedupingPredicate implements Predicate<Entry<Key, Value>> {

    protected final Set<String> uids;
    private final Text holder;

    public DedupingPredicate() {
        uids = Sets.newHashSetWithExpectedSize(64);
        holder = new Text();
    }

    @Override
    public boolean apply(Entry<Key, Value> input) {
        Preconditions.checkNotNull(input);
        Preconditions.checkNotNull(input.getKey());

        input.getKey().getColumnQualifier(holder);

        int index = holder.find(Defaults.NULL_BYTE_STR);

        Preconditions.checkArgument(-1 != index);

        String uid = null;
        try {
            uid = Text.decode(holder.getBytes(), index + 1, holder.getLength() - (index + 1));
        } catch (CharacterCodingException e) {
            throw new RuntimeException(e);
        }

        // If we haven't seen this UID yet, note such, and then keep this item
        if (!uids.contains(uid)) {
            uids.add(uid);
            return true;
        }

        // Otherwise, don't re-return this item
        return false;
    }

}