Github user joshelser commented on a diff in the pull request:
https://github.com/apache/accumulo/pull/224#discussion_r105247239
--- Diff:
server/tserver/src/main/java/org/apache/accumulo/tserver/compaction/strategies/TooManyDeletesCompactionStrategy.java
---
@@ -0,0 +1,173 @@
+/*
+ * 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.tserver.compaction.strategies;
+
+import static
org.apache.accumulo.core.client.summary.summarizers.DeletesSummarizer.DELETES_STAT;
+import static
org.apache.accumulo.core.client.summary.summarizers.DeletesSummarizer.TOTAL_STAT;
+
+import java.io.IOException;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.function.Predicate;
+
+import org.apache.accumulo.core.client.mapred.AccumuloFileOutputFormat;
+import org.apache.accumulo.core.client.rfile.RFile.WriterOptions;
+import org.apache.accumulo.core.client.summary.SummarizerConfiguration;
+import org.apache.accumulo.core.client.summary.Summary;
+import
org.apache.accumulo.core.client.summary.summarizers.DeletesSummarizer;
+import org.apache.accumulo.core.metadata.schema.DataFileValue;
+import org.apache.accumulo.server.fs.FileRef;
+import org.apache.accumulo.tserver.compaction.CompactionPlan;
+import org.apache.accumulo.tserver.compaction.DefaultCompactionStrategy;
+import org.apache.accumulo.tserver.compaction.MajorCompactionRequest;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * This compaction strategy works in concert with the {@link
DeletesSummarizer}. Using the statistics from DeleteSummarizer this strategy
will compact all files
+ * in a table when the number of deletes/non-deletes exceeds a threshold.
+ *
+ * <p>
+ * This strategy has two options. First the {@value #THRESHOLD_OPT} option
allows setting the point at which a compaction will be triggered. This options
+ * defaults to {@value #THRESHOLD_OPT_DEFAULT} and must be in the range
(0.0, 1.0]. The second option is {@value #PROCEED_ZERO_NO_SUMMARY_OPT} which
determines
+ * if the strategy should proceed when a bulk imported file has no summary
information.
+ *
+ * <p>
+ * If the delete summarizer was configured on a table that already had
files, then those files will have not summary information. This strategy can
still
+ * proceed in this situation. It will fall back to using Accumulo's
estimated entires per file in this case. For the files without summary
information the
+ * estimated number of deletes will be zero. This fall back method will
underestimate deletes which will not lead to false positives, except for the
case of
+ * bulk imported files. Accumulo estimates that bulk imported files have
zero entires. The second option {@value #PROCEED_ZERO_NO_SUMMARY_OPT}
determines if
+ * this strategy should proceed when it sees bulk imported files that do
not have summary data. This option defaults to
+ * {@value #PROCEED_ZERO_NO_SUMMARY_OPT_DEFAULT}.
+ *
+ * <p>
+ * Bulk files can be generated with summary information by calling
+ * {@link
AccumuloFileOutputFormat#setSummarizers(org.apache.hadoop.mapred.JobConf,
SummarizerConfiguration...)} or
+ * {@link WriterOptions#withSummarizers(SummarizerConfiguration...)}
+ *
+ * <p>
+ * When this strategy does not decide to compact based on the number of
deletes, then it will defer the decision to the {@link
DefaultCompactionStrategy}.
+ *
+ * <p>
+ * Configuring this compaction strategy for a table will cause it to
always queue compactions, even though it may not decide to compact. These queued
+ * compactions may show up on the Accumulo monitor page. This is because
summary data can not be read until after compaction is queued and dequeued.
When the
+ * compaction is dequeued it can then decide not to compact. See <a
href=https://issues.apache.org/jira/browse/ACCUMULO-4573>ACCUMULO-4573</a>
+ *
+ * @since 2.0.0
+ */
+public class TooManyDeletesCompactionStrategy extends
DefaultCompactionStrategy {
--- End diff --
I can't adequately express how cool I think this is.
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