mirror of https://gitee.com/bigwinds/arangodb
130 lines
3.8 KiB
C++
130 lines
3.8 KiB
C++
////////////////////////////////////////////////////////////////////////////////
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/// DISCLAIMER
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///
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/// Copyright 2014-2016 ArangoDB GmbH, Cologne, Germany
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/// Copyright 2004-2014 triAGENS GmbH, Cologne, Germany
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///
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/// Licensed under the Apache License, Version 2.0 (the "License");
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/// you may not use this file except in compliance with the License.
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/// You may obtain a copy of the License at
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///
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/// http://www.apache.org/licenses/LICENSE-2.0
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///
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/// Unless required by applicable law or agreed to in writing, software
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/// distributed under the License is distributed on an "AS IS" BASIS,
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/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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/// See the License for the specific language governing permissions and
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/// limitations under the License.
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///
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/// Copyright holder is ArangoDB GmbH, Cologne, Germany
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///
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/// @author Jan Steemann
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////////////////////////////////////////////////////////////////////////////////
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#include "ClusterSelectivityEstimates.h"
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#include "Basics/ReadLocker.h"
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#include "Basics/WriteLocker.h"
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#include "Cluster/ClusterMethods.h"
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#include "Indexes/Index.h"
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#include "VocBase/LogicalCollection.h"
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using namespace arangodb;
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ClusterSelectivityEstimates::ClusterSelectivityEstimates(LogicalCollection& collection)
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: _collection(collection),
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_expireStamp(0.0) {}
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void ClusterSelectivityEstimates::flush() {
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WRITE_LOCKER(lock, _lock);
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_estimates.clear();
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_expireStamp = 0.0;
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}
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std::unordered_map<std::string, double> ClusterSelectivityEstimates::get(bool allowUpdate) const {
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double now;
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{
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READ_LOCKER(readLock, _lock);
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if (!allowUpdate) {
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// return whatever is there. may be empty as well
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return _estimates;
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}
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now = TRI_microtime();
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if (!_estimates.empty() && _expireStamp > now) {
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// already have an estimate, and it is not yet expired
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return _estimates;
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}
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}
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// have no estimate yet, or it is already expired
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// we have given up the read lock here
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// because we now need to modify the estimates
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int tries = 0;
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while (true) {
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decltype(_estimates) estimates;
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WRITE_LOCKER(writeLock, _lock);
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if (!_estimates.empty() && _expireStamp > now) {
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// some other thread has updated the estimates for us... just use them
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return _estimates;
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}
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int res = selectivityEstimatesOnCoordinator(_collection.vocbase().name(), _collection.name(), estimates);
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if (res == TRI_ERROR_NO_ERROR) {
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_estimates = estimates;
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// let selectivity estimates expire less seldom for system collections
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_expireStamp = now + defaultTtl * (_collection.name()[0] == '_' ? 10.0 : 1.0);
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// give up the lock, and then update the selectivity values for each index
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writeLock.unlock();
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// push new selectivity values into indexes' cache
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auto indexes = _collection.getIndexes();
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for (std::shared_ptr<Index>& idx : indexes) {
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auto it = estimates.find(std::to_string(idx->id()));
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if (it != estimates.end()) {
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idx->updateClusterSelectivityEstimate(it->second);
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}
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}
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return estimates;
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}
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if (++tries == 3) {
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return _estimates;
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}
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}
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}
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void ClusterSelectivityEstimates::set(std::unordered_map<std::string, double>&& estimates) {
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double const now = TRI_microtime();
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// push new selectivity values into indexes' cache
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auto indexes = _collection.getIndexes();
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for (std::shared_ptr<Index>& idx : indexes) {
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auto it = estimates.find(std::to_string(idx->id()));
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if (it != estimates.end()) {
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idx->updateClusterSelectivityEstimate(it->second);
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}
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}
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// finally update the cache
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{
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WRITE_LOCKER(writelock, _lock);
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_estimates = std::move(estimates);
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// let selectivity estimates expire less seldom for system collections
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_expireStamp = now + defaultTtl * (_collection.name()[0] == '_' ? 10.0 : 1.0);
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}
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}
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