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leveldb-amulet/util/histogram.h
Hans Wennborg 36a5f8ed7f A number of fixes:
- Replace raw slice comparison with a call to user comparator.
  Added test for custom comparators.

- Fix end of namespace comments.

- Fixed bug in picking inputs for a level-0 compaction.

  When finding overlapping files, the covered range may expand
  as files are added to the input set.  We now correctly expand
  the range when this happens instead of continuing to use the
  old range.  For example, suppose L0 contains files with the
  following ranges:

      F1: a .. d
      F2:    c .. g
      F3:       f .. j

  and the initial compaction target is F3.  We used to search
  for range f..j which yielded {F2,F3}.  However we now expand
  the range as soon as another file is added.  In this case,
  when F2 is added, we expand the range to c..j and restart the
  search.  That picks up file F1 as well.

  This change fixes a bug related to deleted keys showing up
  incorrectly after a compaction as described in Issue 44.

(Sync with upstream @25072954)
2011-10-31 17:22:06 +00:00

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// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
#ifndef STORAGE_LEVELDB_UTIL_HISTOGRAM_H_
#define STORAGE_LEVELDB_UTIL_HISTOGRAM_H_
#include <string>
namespace leveldb {
class Histogram {
public:
Histogram() { }
~Histogram() { }
void Clear();
void Add(double value);
void Merge(const Histogram& other);
std::string ToString() const;
private:
double min_;
double max_;
double num_;
double sum_;
double sum_squares_;
enum { kNumBuckets = 154 };
static const double kBucketLimit[kNumBuckets];
double buckets_[kNumBuckets];
double Median() const;
double Percentile(double p) const;
double Average() const;
double StandardDeviation() const;
};
} // namespace leveldb
#endif // STORAGE_LEVELDB_UTIL_HISTOGRAM_H_