28c82ff1b3
Summary: This diff adds three sets of APIs to RocksDB. = GetColumnFamilyMetaData = * This APIs allow users to obtain the current state of a RocksDB instance on one column family. * See GetColumnFamilyMetaData in include/rocksdb/db.h = EventListener = * A virtual class that allows users to implement a set of call-back functions which will be called when specific events of a RocksDB instance happens. * To register EventListener, simply insert an EventListener to ColumnFamilyOptions::listeners = CompactFiles = * CompactFiles API inputs a set of file numbers and an output level, and RocksDB will try to compact those files into the specified level. = Example = * Example code can be found in example/compact_files_example.cc, which implements a simple external compactor using EventListener, GetColumnFamilyMetaData, and CompactFiles API. Test Plan: listener_test compactor_test example/compact_files_example export ROCKSDB_TESTS=CompactFiles db_test export ROCKSDB_TESTS=MetaData db_test Reviewers: ljin, igor, rven, sdong Reviewed By: sdong Subscribers: MarkCallaghan, dhruba, leveldb Differential Revision: https://reviews.facebook.net/D24705
72 lines
2.7 KiB
C++
72 lines
2.7 KiB
C++
// Copyright (c) 2013, Facebook, Inc. All rights reserved.
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// This source code is licensed under the BSD-style license found in the
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// LICENSE file in the root directory of this source tree. An additional grant
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// of patent rights can be found in the PATENTS file in the same directory.
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// 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_INCLUDE_COMPARATOR_H_
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#define STORAGE_ROCKSDB_INCLUDE_COMPARATOR_H_
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#include <string>
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namespace rocksdb {
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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 rocksdb 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 "rocksdb." 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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// Return a builtin comparator that uses reverse lexicographic byte-wise
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// ordering.
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extern const Comparator* ReverseBytewiseComparator();
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} // namespace rocksdb
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#endif // STORAGE_ROCKSDB_INCLUDE_COMPARATOR_H_
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