ceph/src/rocksdb/include/rocksdb/universal_compaction.h

   1 // Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
   2 //  This source code is licensed under both the GPLv2 (found in the
   3 //  COPYING file in the root directory) and Apache 2.0 License
   4 //  (found in the LICENSE.Apache file in the root directory).
   5
   6 #pragma once
   7
   8 #include <stdint.h>
   9 #include <climits>
  10 #include <vector>
  11
  12 namespace rocksdb {
  13
  14 //
  15 // Algorithm used to make a compaction request stop picking new files
  16 // into a single compaction run
  17 //
  18 enum CompactionStopStyle {
  19   kCompactionStopStyleSimilarSize,  // pick files of similar size
  20   kCompactionStopStyleTotalSize     // total size of picked files > next file
  21 };
  22
  23 class CompactionOptionsUniversal {
  24  public:
  25   // Percentage flexibility while comparing file size. If the candidate file(s)
  26   // size is 1% smaller than the next file's size, then include next file into
  27   // this candidate set. // Default: 1
  28   unsigned int size_ratio;
  29
  30   // The minimum number of files in a single compaction run. Default: 2
  31   unsigned int min_merge_width;
  32
  33   // The maximum number of files in a single compaction run. Default: UINT_MAX
  34   unsigned int max_merge_width;
  35
  36   // The size amplification is defined as the amount (in percentage) of
  37   // additional storage needed to store a single byte of data in the database.
  38   // For example, a size amplification of 2% means that a database that
  39   // contains 100 bytes of user-data may occupy upto 102 bytes of
  40   // physical storage. By this definition, a fully compacted database has
  41   // a size amplification of 0%. Rocksdb uses the following heuristic
  42   // to calculate size amplification: it assumes that all files excluding
  43   // the earliest file contribute to the size amplification.
  44   // Default: 200, which means that a 100 byte database could require upto
  45   // 300 bytes of storage.
  46   unsigned int max_size_amplification_percent;
  47
  48   // If this option is set to be -1 (the default value), all the output files
  49   // will follow compression type specified.
  50   //
  51   // If this option is not negative, we will try to make sure compressed
  52   // size is just above this value. In normal cases, at least this percentage
  53   // of data will be compressed.
  54   // When we are compacting to a new file, here is the criteria whether
  55   // it needs to be compressed: assuming here are the list of files sorted
  56   // by generation time:
  57   //    A1...An B1...Bm C1...Ct
  58   // where A1 is the newest and Ct is the oldest, and we are going to compact
  59   // B1...Bm, we calculate the total size of all the files as total_size, as
  60   // well as  the total size of C1...Ct as total_C, the compaction output file
  61   // will be compressed iff
  62   //   total_C / total_size < this percentage
  63   // Default: -1
  64   int compression_size_percent;
  65
  66   // The algorithm used to stop picking files into a single compaction run
  67   // Default: kCompactionStopStyleTotalSize
  68   CompactionStopStyle stop_style;
  69
  70   // Option to optimize the universal multi level compaction by enabling
  71   // trivial move for non overlapping files.
  72   // Default: false
  73   bool allow_trivial_move;
  74
  75   // Default set of parameters
  76   CompactionOptionsUniversal()
  77       : size_ratio(1),
  78         min_merge_width(2),
  79         max_merge_width(UINT_MAX),
  80         max_size_amplification_percent(200),
  81         compression_size_percent(-1),
  82         stop_style(kCompactionStopStyleTotalSize),
  83         allow_trivial_move(false) {}
  84 };
  85
  86 }  // namespace rocksdb