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36a5f8ed7f
- 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)
64 lines
2.3 KiB
C++
64 lines
2.3 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_LEVELDB_INCLUDE_COMPARATOR_H_
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#define STORAGE_LEVELDB_INCLUDE_COMPARATOR_H_
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#include <string>
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namespace leveldb {
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class Slice;
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// A Comparator object provides a total order across slices that are
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// used as keys in an sstable or a database. A Comparator implementation
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// must be thread-safe since leveldb may invoke its methods concurrently
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// from multiple threads.
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class Comparator {
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public:
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virtual ~Comparator();
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// Three-way comparison. Returns value:
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// < 0 iff "a" < "b",
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// == 0 iff "a" == "b",
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// > 0 iff "a" > "b"
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virtual int Compare(const Slice& a, const Slice& b) const = 0;
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// The name of the comparator. Used to check for comparator
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// mismatches (i.e., a DB created with one comparator is
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// accessed using a different comparator.
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//
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// The client of this package should switch to a new name whenever
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// the comparator implementation changes in a way that will cause
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// the relative ordering of any two keys to change.
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//
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// Names starting with "leveldb." are reserved and should not be used
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// by any clients of this package.
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virtual const char* Name() const = 0;
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// Advanced functions: these are used to reduce the space requirements
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// for internal data structures like index blocks.
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// If *start < limit, changes *start to a short string in [start,limit).
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// Simple comparator implementations may return with *start unchanged,
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// i.e., an implementation of this method that does nothing is correct.
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virtual void FindShortestSeparator(
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std::string* start,
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const Slice& limit) const = 0;
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// Changes *key to a short string >= *key.
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// Simple comparator implementations may return with *key unchanged,
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// i.e., an implementation of this method that does nothing is correct.
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virtual void FindShortSuccessor(std::string* key) const = 0;
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};
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// Return a builtin comparator that uses lexicographic byte-wise
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// ordering. The result remains the property of this module and
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// must not be deleted.
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extern const Comparator* BytewiseComparator();
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} // namespace leveldb
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#endif // STORAGE_LEVELDB_INCLUDE_COMPARATOR_H_
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