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 <climits>
   9 #include <cstdint>
  10 #include <vector>
  11
  12 #include "rocksdb/rocksdb_namespace.h"
  13
  14 namespace ROCKSDB_NAMESPACE {
  15
  16 //
  17 // Algorithm used to make a compaction request stop picking new files
  18 // into a single compaction run
  19 //
  20 enum CompactionStopStyle {
  21   kCompactionStopStyleSimilarSize,  // pick files of similar size
  22   kCompactionStopStyleTotalSize     // total size of picked files > next file
  23 };
  24
  25 class CompactionOptionsUniversal {
  26  public:
  27   // Percentage flexibility while comparing file size. If the candidate file(s)
  28   // size is 1% smaller than the next file's size, then include next file into
  29   // this candidate set. // Default: 1
  30   unsigned int size_ratio;
  31
  32   // The minimum number of files in a single compaction run. Default: 2
  33   unsigned int min_merge_width;
  34
  35   // The maximum number of files in a single compaction run. Default: UINT_MAX
  36   unsigned int max_merge_width;
  37
  38   // The size amplification is defined as the amount (in percentage) of
  39   // additional storage needed to store a single byte of data in the database.
  40   // For example, a size amplification of 2% means that a database that
  41   // contains 100 bytes of user-data may occupy up to 102 bytes of
  42   // physical storage. By this definition, a fully compacted database has
  43   // a size amplification of 0%. Rocksdb uses the following heuristic
  44   // to calculate size amplification: it assumes that all files excluding
  45   // the earliest file contribute to the size amplification.
  46   // Default: 200, which means that a 100 byte database could require up to
  47   // 300 bytes of storage.
  48   unsigned int max_size_amplification_percent;
  49
  50   // If this option is set to be -1 (the default value), all the output files
  51   // will follow compression type specified.
  52   //
  53   // If this option is not negative, we will try to make sure compressed
  54   // size is just above this value. In normal cases, at least this percentage
  55   // of data will be compressed.
  56   // When we are compacting to a new file, here is the criteria whether
  57   // it needs to be compressed: assuming here are the list of files sorted
  58   // by generation time:
  59   //    A1...An B1...Bm C1...Ct
  60   // where A1 is the newest and Ct is the oldest, and we are going to compact
  61   // B1...Bm, we calculate the total size of all the files as total_size, as
  62   // well as the total size of C1...Ct as total_C, the compaction output file
  63   // will be compressed iff
  64   //   total_C / total_size < this percentage
  65   // Default: -1
  66   int compression_size_percent;
  67
  68   // The algorithm used to stop picking files into a single compaction run
  69   // Default: kCompactionStopStyleTotalSize
  70   CompactionStopStyle stop_style;
  71
  72   // Option to optimize the universal multi level compaction by enabling
  73   // trivial move for non overlapping files.
  74   // Default: false
  75   bool allow_trivial_move;
  76
  77   // EXPERIMENTAL
  78   // If true, try to limit compaction size under max_compaction_bytes.
  79   // This might cause higher write amplification, but can prevent some
  80   // problem caused by large compactions.
  81   // Default: false
  82   bool incremental;
  83
  84   // Default set of parameters
  85   CompactionOptionsUniversal()
  86       : size_ratio(1),
  87         min_merge_width(2),
  88         max_merge_width(UINT_MAX),
  89         max_size_amplification_percent(200),
  90         compression_size_percent(-1),
  91         stop_style(kCompactionStopStyleTotalSize),
  92         allow_trivial_move(false),
  93         incremental(false) {}
  94 };
  95
  96 }  // namespace ROCKSDB_NAMESPACE