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From: joshelser <git@git.apache.org>
To: dev@accumulo.apache.org
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Subject: [GitHub] accumulo pull request #224: ACCUMULO-4500 ACCUMULO-96 Added summarization
Content-Type: text/plain
Message-Id: <20170307005011.608E4E980E@git1-us-west.apache.org>
Date: Tue,  7 Mar 2017 00:50:11 +0000 (UTC)
archived-at: Tue, 07 Mar 2017 00:50:14 -0000

Github user joshelser commented on a diff in the pull request:

    https://github.com/apache/accumulo/pull/224#discussion_r104508413
  
    --- Diff: core/src/main/java/org/apache/accumulo/core/client/summary/summarizers/DeletesSummarizer.java ---
    @@ -0,0 +1,75 @@
    +/*
    + * 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.
    + */
    +
    +package org.apache.accumulo.core.client.summary.summarizers;
    +
    +import org.apache.accumulo.core.client.admin.TableOperations;
    +import org.apache.accumulo.core.client.summary.Summarizer;
    +import org.apache.accumulo.core.client.summary.SummarizerConfiguration;
    +import org.apache.accumulo.core.data.Key;
    +import org.apache.accumulo.core.data.Value;
    +
    +/**
    + * This summarizer tracks the total number of delete Keys seen and the total number of keys seen.
    + *
    + * <p>
    + * This summarizer is used by org.apache.accumulo.tserver.compaction.strategies.TooManyDeletesCompactionStrategy to make compaction decisions based on the
    + * number of deletes.
    + *
    + * @since 2.0.0
    + * @see TableOperations#addSummarizers(String, org.apache.accumulo.core.client.summary.SummarizerConfiguration...)
    + */
    +public class DeletesSummarizer implements Summarizer {
    +
    +  /**
    +   * The name of the statistics for the number of deletes.
    +   */
    +  public static final String DELETES_STAT = "deletes";
    +
    +  /**
    +   * The name of the statistics for the total number of keys.
    +   */
    +  public static final String TOTAL_STAT = "total";
    +
    +  @Override
    +  public Collector collector(SummarizerConfiguration sc) {
    +    return new Collector() {
    +
    +      long total = 0;
    +      long deletes = 0;
    +
    +      @Override
    +      public void accept(Key k, Value v) {
    +        total++;
    +        if (k.isDeleted()) {
    +          deletes++;
    +        }
    +      }
    +
    +      @Override
    +      public void summarize(StatisticConsumer sc) {
    +        sc.accept(DELETES_STAT, deletes);
    +        sc.accept(TOTAL_STAT, total);
    +      }
    +    };
    +  }
    +
    +  @Override
    +  public Combiner combiner(SummarizerConfiguration sc) {
    +    return (m1, m2) -> m2.forEach((k, v) -> m1.merge(k, v, Long::sum));
    --- End diff --
    
    This seems like a common case for Summarizers. Would it make sense to lift this into an `abstract class LongSummarizer`?
    
    ```java
    public abstract class LongSummarizer implements Summarizer {
      @Override
      public Combiner combiner(SummarizerConfiguration sc) {
        return (m1, m2) -> m2.forEach((k, v) -> m1.merge(k, v, Long::sum));
      }
    }
    ```
    
    Then, make this class..
    
    ```java
    public class DeletesSummarizer extends LongSummarizer {
    ...
    }
    ```


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