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/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include "mongo/base/string_data.h"
#include "mongo/bson/bsonobj.h"
#include "mongo/platform/atomic_word.h"
#include "mongo/util/string_map.h"
#include "mongo/util/time_support.h"
namespace mongo {
class ClockSource;
/**
* CollectionIndexUsageTracker tracks index usage statistics for a collection. An index is
* considered "used" when it appears as part of a winning plan for an operation that uses the
* query system.
*
* Indexes must be registered and deregistered on creation/destruction.
*/
class CollectionIndexUsageTracker {
CollectionIndexUsageTracker(const CollectionIndexUsageTracker&) = delete;
CollectionIndexUsageTracker& operator=(const CollectionIndexUsageTracker&) = delete;
public:
struct IndexUsageStats {
IndexUsageStats() = default;
explicit IndexUsageStats(Date_t now, const BSONObj& key)
: trackerStartTime(now), indexKey(key.getOwned()) {}
IndexUsageStats(const IndexUsageStats& other)
: accesses(other.accesses.load()),
trackerStartTime(other.trackerStartTime),
indexKey(other.indexKey) {}
IndexUsageStats& operator=(const IndexUsageStats& other) {
accesses.store(other.accesses.load());
trackerStartTime = other.trackerStartTime;
indexKey = other.indexKey;
return *this;
}
// Number of operations that have used this index.
AtomicWord<long long> accesses;
// Date/Time that we started tracking index usage.
Date_t trackerStartTime;
// An owned copy of the associated IndexDescriptor's index key.
BSONObj indexKey;
};
/**
* Constructs a CollectionIndexUsageTracker.
*
* Does not take ownership of 'clockSource'. 'clockSource' must refer to a non-null clock
* source that is valid for the lifetime of the constructed CollectionIndexUsageTracker.
*/
explicit CollectionIndexUsageTracker(ClockSource* clockSource);
/**
* Record that an operation used index 'indexName'. Safe to be called by multiple threads
* concurrently.
*/
void recordIndexAccess(StringData indexName);
/**
* Add map entry for 'indexName' stats collection. Must be called under exclusive collection
* lock.
*/
void registerIndex(StringData indexName, const BSONObj& indexKey);
/**
* Erase statistics for index 'indexName'. Must be called under exclusive collection lock.
* Can be called even if indexName is not registered. This is possible under certain failure
* scenarios.
*/
void unregisterIndex(StringData indexName);
/**
* Get the current state of the usage statistics map. This map will only include indexes that
* exist at the time of calling. Must be called while holding the collection lock in any mode.
*/
StringMap<CollectionIndexUsageTracker::IndexUsageStats> getUsageStats() const;
private:
// Map from index name to usage statistics.
StringMap<CollectionIndexUsageTracker::IndexUsageStats> _indexUsageMap;
// Clock source. Used when the 'trackerStartTime' time for an IndexUsageStats object needs to
// be set.
ClockSource* _clockSource;
};
typedef StringMap<CollectionIndexUsageTracker::IndexUsageStats> CollectionIndexUsageMap;
} // namespace mongo
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