Revision 98421774b6c71cc6ee092240374c2453d2d03e43 authored by Ankit Gupta on 15 April 2014, 04:14:29 UTC, committed by Ankit Gupta on 15 April 2014, 04:14:29 UTC
1 parent 8756a32
compaction_filter.h
// Copyright (c) 2013, Facebook, Inc. All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same directory.
// Copyright (c) 2013 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_ROCKSDB_INCLUDE_COMPACTION_FILTER_H_
#define STORAGE_ROCKSDB_INCLUDE_COMPACTION_FILTER_H_
#include <string>
#include <vector>
namespace rocksdb {
class Slice;
class SliceTransform;
// Context information of a compaction run
struct CompactionFilterContext {
// Does this compaction run include all data files
bool is_full_compaction;
// Is this compaction requested by the client (true),
// or is it occurring as an automatic compaction process
bool is_manual_compaction;
};
// CompactionFilter allows an application to modify/delete a key-value at
// the time of compaction.
class CompactionFilter {
public:
// Context information of a compaction run
struct Context {
// Does this compaction run include all data files
bool is_full_compaction;
// Is this compaction requested by the client (true),
// or is it occurring as an automatic compaction process
bool is_manual_compaction;
};
virtual ~CompactionFilter() {}
// The compaction process invokes this
// method for kv that is being compacted. A return value
// of false indicates that the kv should be preserved in the
// output of this compaction run and a return value of true
// indicates that this key-value should be removed from the
// output of the compaction. The application can inspect
// the existing value of the key and make decision based on it.
//
// When the value is to be preserved, the application has the option
// to modify the existing_value and pass it back through new_value.
// value_changed needs to be set to true in this case.
//
// If multithreaded compaction is being used *and* a single CompactionFilter
// instance was supplied via Options::compaction_filter, this method may be
// called from different threads concurrently. The application must ensure
// that the call is thread-safe.
//
// If the CompactionFilter was created by a factory, then it will only ever
// be used by a single thread that is doing the compaction run, and this
// call does not need to be thread-safe. However, multiple filters may be
// in existence and operating concurrently.
virtual bool Filter(int level,
const Slice& key,
const Slice& existing_value,
std::string* new_value,
bool* value_changed) const = 0;
// Returns a name that identifies this compaction filter.
// The name will be printed to LOG file on start up for diagnosis.
virtual const char* Name() const = 0;
};
// CompactionFilterV2 that buffers kv pairs sharing the same prefix and let
// application layer to make individual decisions for all the kv pairs in the
// buffer.
class CompactionFilterV2 {
public:
virtual ~CompactionFilterV2() {}
// The compaction process invokes this method for all the kv pairs
// sharing the same prefix. It is a "roll-up" version of CompactionFilter.
//
// Each entry in the return vector indicates if the corresponding kv should
// be preserved in the output of this compaction run. The application can
// inspect the exisitng values of the keys and make decision based on it.
//
// When a value is to be preserved, the application has the option
// to modify the entry in existing_values and pass it back through an entry
// in new_values. A corresponding values_changed entry needs to be set to
// true in this case. Note that the new_values vector contains only changed
// values, i.e. new_values.size() <= values_changed.size().
//
typedef std::vector<Slice> SliceVector;
virtual std::vector<bool> Filter(int level,
const SliceVector& keys,
const SliceVector& existing_values,
std::vector<std::string>* new_values,
std::vector<bool>* values_changed)
const = 0;
// Returns a name that identifies this compaction filter.
// The name will be printed to LOG file on start up for diagnosis.
virtual const char* Name() const = 0;
};
// Each compaction will create a new CompactionFilter allowing the
// application to know about different campactions
class CompactionFilterFactory {
public:
virtual ~CompactionFilterFactory() { }
virtual std::unique_ptr<CompactionFilter> CreateCompactionFilter(
const CompactionFilter::Context& context) = 0;
// Returns a name that identifies this compaction filter factory.
virtual const char* Name() const = 0;
};
// Default implementaion of CompactionFilterFactory which does not
// return any filter
class DefaultCompactionFilterFactory : public CompactionFilterFactory {
public:
virtual std::unique_ptr<CompactionFilter> CreateCompactionFilter(
const CompactionFilter::Context& context) override {
return std::unique_ptr<CompactionFilter>(nullptr);
}
virtual const char* Name() const override {
return "DefaultCompactionFilterFactory";
}
};
// Each compaction will create a new CompactionFilterV2
//
// CompactionFilterFactoryV2 enables application to specify a prefix and use
// CompactionFilterV2 to filter kv-pairs in batches. Each batch contains all
// the kv-pairs sharing the same prefix.
//
// This is useful for applications that require grouping kv-pairs in
// compaction filter to make a purge/no-purge decision. For example, if the
// key prefix is user id and the rest of key represents the type of value.
// This batching filter will come in handy if the application's compaction
// filter requires knowledge of all types of values for any user id.
//
class CompactionFilterFactoryV2 {
public:
// NOTE: CompactionFilterFactoryV2 will not delete prefix_extractor
explicit CompactionFilterFactoryV2(const SliceTransform* prefix_extractor)
: prefix_extractor_(prefix_extractor) { }
virtual ~CompactionFilterFactoryV2() { }
virtual std::unique_ptr<CompactionFilterV2> CreateCompactionFilterV2(
const CompactionFilterContext& context) = 0;
// Returns a name that identifies this compaction filter factory.
virtual const char* Name() const = 0;
const SliceTransform* GetPrefixExtractor() const {
return prefix_extractor_;
}
void SetPrefixExtractor(const SliceTransform* prefix_extractor) {
prefix_extractor_ = prefix_extractor;
}
private:
// Prefix extractor for compaction filter v2
// Keys sharing the same prefix will be buffered internally.
// Client can implement a Filter callback function to operate on the buffer
const SliceTransform* prefix_extractor_;
};
// Default implementaion of CompactionFilterFactoryV2 which does not
// return any filter
class DefaultCompactionFilterFactoryV2 : public CompactionFilterFactoryV2 {
public:
explicit DefaultCompactionFilterFactoryV2()
: CompactionFilterFactoryV2(nullptr) { }
virtual std::unique_ptr<CompactionFilterV2>
CreateCompactionFilterV2(
const CompactionFilterContext& context) override {
return std::unique_ptr<CompactionFilterV2>(nullptr);
}
virtual const char* Name() const override {
return "DefaultCompactionFilterFactoryV2";
}
};
} // namespace rocksdb
#endif // STORAGE_ROCKSDB_INCLUDE_COMPACTION_FILTER_H_
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