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Summary: This patch adds a option for universal compaction to allow us to only compress output files if the files compacted previously did not yet reach a specified ratio, to save CPU costs in some cases. Compression is always skipped for flushing. This is because the size information is not easy to evaluate for flushing case. We can improve it later. Test Plan: add test DBTest.UniversalCompactionCompressRatio1 and DBTest.UniversalCompactionCompressRatio12 Reviewers: dhruba, haobo Reviewed By: dhruba CC: leveldb Differential Revision: https://reviews.facebook.net/D13467
89 lines
3.3 KiB
C++
89 lines
3.3 KiB
C++
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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#ifndef STORAGE_ROCKSDB_UNIVERSAL_COMPACTION_OPTIONS_H
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#define STORAGE_ROCKSDB_UNIVERSAL_COMPACTION_OPTIONS_H
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#include <stddef.h>
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#include <string>
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#include <memory>
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#include <vector>
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#include <stdint.h>
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#include <climits>
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#include "rocksdb/slice.h"
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#include "rocksdb/statistics.h"
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namespace rocksdb {
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//
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// Algorithm used to make a compaction request stop picking new files
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// into a single compaction run
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//
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enum CompactionStopStyle {
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kCompactionStopStyleSimilarSize, // pick files of similar size
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kCompactionStopStyleTotalSize // total size of picked files > next file
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};
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class CompactionOptionsUniversal {
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public:
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// Percentage flexibilty while comparing file size. If the candidate file(s)
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// size is 1% smaller than the next file's size, then include next file into
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// this candidate set. // Default: 1
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unsigned int size_ratio;
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// The minimum number of files in a single compaction run. Default: 2
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unsigned int min_merge_width;
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// The maximum number of files in a single compaction run. Default: UINT_MAX
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unsigned int max_merge_width;
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// The size amplification is defined as the amount (in percentage) of
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// additional storage needed to store a single byte of data in the database.
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// For example, a size amplification of 2% means that a database that
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// contains 100 bytes of user-data may occupy upto 102 bytes of
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// physical storage. By this definition, a fully compacted database has
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// a size amplification of 0%. Rocksdb uses the following heuristic
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// to calculate size amplification: it assumes that all files excluding
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// the earliest file contribute to the size amplification.
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// Default: 200, which means that a 100 byte database could require upto
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// 300 bytes of storage.
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unsigned int max_size_amplification_percent;
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// If this option is set to be -1 (the default value), all the output files
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// will follow compression type specified.
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//
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// If this option is not negative, we will try to make sure compressed
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// size is just above this value. In normal cases, at least this percentage
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// of data will be compressed.
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// When we are compacting to a new file, here is the criteria whether
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// it needs to be compressed: assuming here are the list of files sorted
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// by generation time:
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// A1...An B1...Bm C1...Ct
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// where A1 is the newest and Ct is the oldest, and we are going to compact
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// B1...Bm, we calculate the total size of all the files as total_size, as
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// well as the total size of C1...Ct as total_C, the compaction output file
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// will be compressed iff
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// total_C / total_size < this percentage
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int compression_size_percent;
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// The algorithm used to stop picking files into a single compaction run
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// Default: kCompactionStopStyleTotalSize
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CompactionStopStyle stop_style;
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// Default set of parameters
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CompactionOptionsUniversal() :
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size_ratio(1),
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min_merge_width(2),
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max_merge_width(UINT_MAX),
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max_size_amplification_percent(200),
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compression_size_percent(-1),
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stop_style(kCompactionStopStyleTotalSize) {
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}
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};
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} // namespace rocksdb
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#endif // STORAGE_ROCKSDB_UNIVERSAL_COMPACTION_OPTIONS_H
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