mirror of https://gitee.com/bigwinds/arangodb
122 lines
3.4 KiB
C++
122 lines
3.4 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 Christoph Uhde
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/// @author Jan Steemann
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////////////////////////////////////////////////////////////////////////////////
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#include "SelectivityEstimates.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 "VocBase/LogicalCollection.h"
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using namespace arangodb;
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ClusterSelectivityEstimates::ClusterSelectivityEstimates(LogicalCollection* collection)
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: _collection(collection), _expires(0.0), _updating(false) {}
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ClusterSelectivityEstimates& ClusterSelectivityEstimates::operator=(ClusterSelectivityEstimates const& other) {
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if (this != &other) {
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WRITE_LOCKER(locker1, _lock);
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READ_LOCKER(locker2, other._lock);
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_collection = other._collection;
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_estimates = other._estimates;
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_expires = other._expires;
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_updating = false;
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}
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return *this;
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}
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ClusterSelectivityEstimates& ClusterSelectivityEstimates::operator=(ClusterSelectivityEstimates&& other) {
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if (this != &other) {
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WRITE_LOCKER(locker1, _lock);
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WRITE_LOCKER(locker2, other._lock);
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_collection = other._collection;
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_estimates = std::move(other._estimates);
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_expires = other._expires;
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_updating = false;
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other._expires = 0.0;
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}
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return *this;
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}
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ClusterSelectivityEstimates::~ClusterSelectivityEstimates() {}
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bool ClusterSelectivityEstimates::defined() const {
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READ_LOCKER(locker, _lock);
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return _expires != 0.0;
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}
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ClusterSelectivityEstimates::ValueType ClusterSelectivityEstimates::fetch() {
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double now = TRI_microtime();
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{
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READ_LOCKER(locker, _lock);
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if (!_estimates.empty() &&
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(now - _expires < defaultExpireTime)) {
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return _estimates;
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}
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// need to fetch an update of the estimates
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}
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while (true) {
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bool weAreUpdating = false;
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{
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WRITE_LOCKER(locker, _lock);
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// re-check update condition
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if (!_estimates.empty() &&
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(now - _expires < defaultExpireTime)) {
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// another thread has updated the estimates
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return _estimates;
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}
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if (!_updating) {
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_updating = true;
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weAreUpdating = true;
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}
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}
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if (weAreUpdating) {
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ValueType estimates;
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selectivityEstimatesOnCoordinator(_collection->vocbase()->name(), _collection->name(), estimates);
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WRITE_LOCKER(locker, _lock);
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_estimates = estimates;
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_expires = now;
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_updating = false;
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return _estimates;
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}
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now = TRI_microtime();
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usleep(10000);
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}
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}
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ClusterSelectivityEstimates::ValueType ClusterSelectivityEstimates::get() const {
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READ_LOCKER(locker, _lock);
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return _estimates;
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}
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