Status CachedPlanStage::pickBestPlan(PlanYieldPolicy* yieldPolicy) {
// Adds the amount of time taken by pickBestPlan() to executionTimeMillis. There's lots of
// execution work that happens here, so this is needed for the time accounting to
// make sense.
ScopedTimer timer(&_commonStats.executionTimeMillis);
// If we work this many times during the trial period, then we will replan the
// query from scratch.
size_t maxWorksBeforeReplan =
static_cast<size_t>(internalQueryCacheEvictionRatio * _decisionWorks);
// The trial period ends without replanning if the cached plan produces this many results.
size_t numResults = MultiPlanStage::getTrialPeriodNumToReturn(*_canonicalQuery);
for (size_t i = 0; i < maxWorksBeforeReplan; ++i) {
// Might need to yield between calls to work due to the timer elapsing.
Status yieldStatus = tryYield(yieldPolicy);
if (!yieldStatus.isOK()) {
return yieldStatus;
}
WorkingSetID id = WorkingSet::INVALID_ID;
PlanStage::StageState state = child()->work(&id);
if (PlanStage::ADVANCED == state) {
// Save result for later.
WorkingSetMember* member = _ws->get(id);
// Ensure that the BSONObj underlying the WorkingSetMember is owned in case we yield.
member->makeObjOwnedIfNeeded();
_results.push_back(id);
if (_results.size() >= numResults) {
// Once a plan returns enough results, stop working. Update cache with stats
// from this run and return.
updatePlanCache();
return Status::OK();
}
} else if (PlanStage::IS_EOF == state) {
// Cached plan hit EOF quickly enough. No need to replan. Update cache with stats
// from this run and return.
updatePlanCache();
return Status::OK();
} else if (PlanStage::NEED_YIELD == state) {
if (id == WorkingSet::INVALID_ID) {
if (!yieldPolicy->allowedToYield()) {
throw WriteConflictException();
}
} else {
WorkingSetMember* member = _ws->get(id);
invariant(member->hasFetcher());
// Transfer ownership of the fetcher and yield.
_fetcher.reset(member->releaseFetcher());
}
if (yieldPolicy->allowedToYield()) {
yieldPolicy->forceYield();
}
Status yieldStatus = tryYield(yieldPolicy);
if (!yieldStatus.isOK()) {
return yieldStatus;
}
} else if (PlanStage::FAILURE == state) {
// On failure, fall back to replanning the whole query. We neither evict the
// existing cache entry nor cache the result of replanning.
BSONObj statusObj;
WorkingSetCommon::getStatusMemberObject(*_ws, id, &statusObj);
LOG(1) << "Execution of cached plan failed, falling back to replan."
<< " query: " << _canonicalQuery->toStringShort()
<< " planSummary: " << Explain::getPlanSummary(child().get())
<< " status: " << statusObj;
const bool shouldCache = false;
return replan(yieldPolicy, shouldCache);
} else if (PlanStage::DEAD == state) {
BSONObj statusObj;
WorkingSetCommon::getStatusMemberObject(*_ws, id, &statusObj);
LOG(1) << "Execution of cached plan failed: PlanStage died"
<< ", query: " << _canonicalQuery->toStringShort()
<< " planSummary: " << Explain::getPlanSummary(child().get())
<< " status: " << statusObj;
return WorkingSetCommon::getMemberObjectStatus(statusObj);
} else {
invariant(PlanStage::NEED_TIME == state);
}
}
// If we're here, the trial period took more than 'maxWorksBeforeReplan' work cycles. This
// plan is taking too long, so we replan from scratch.
LOG(1) << "Execution of cached plan required " << maxWorksBeforeReplan
<< " works, but was originally cached with only " << _decisionWorks
<< " works. Evicting cache entry and replanning query: "
<< _canonicalQuery->toStringShort()
<< " plan summary before replan: " << Explain::getPlanSummary(child().get());
const bool shouldCache = true;
return replan(yieldPolicy, shouldCache);
}
Status CachedPlanStage::pickBestPlan(PlanYieldPolicy* yieldPolicy) {
// Adds the amount of time taken by pickBestPlan() to executionTimeMillis. There's lots of
// execution work that happens here, so this is needed for the time accounting to
// make sense.
ScopedTimer timer(getClock(), &_commonStats.executionTimeMillis);
// During plan selection, the list of indices we are using to plan must remain stable, so the
// query will die during yield recovery if any index has been dropped. However, once plan
// selection completes successfully, we no longer need all indices to stick around. The selected
// plan should safely die on yield recovery if it is using the dropped index.
//
// Dismiss the requirement that no indices can be dropped when this method returns.
ON_BLOCK_EXIT([this] { releaseAllIndicesRequirement(); });
// If we work this many times during the trial period, then we will replan the
// query from scratch.
size_t maxWorksBeforeReplan =
static_cast<size_t>(internalQueryCacheEvictionRatio * _decisionWorks);
// The trial period ends without replanning if the cached plan produces this many results.
size_t numResults = MultiPlanStage::getTrialPeriodNumToReturn(*_canonicalQuery);
for (size_t i = 0; i < maxWorksBeforeReplan; ++i) {
// Might need to yield between calls to work due to the timer elapsing.
Status yieldStatus = tryYield(yieldPolicy);
if (!yieldStatus.isOK()) {
return yieldStatus;
}
WorkingSetID id = WorkingSet::INVALID_ID;
PlanStage::StageState state = child()->work(&id);
if (PlanStage::ADVANCED == state) {
// Save result for later.
WorkingSetMember* member = _ws->get(id);
// Ensure that the BSONObj underlying the WorkingSetMember is owned in case we yield.
member->makeObjOwnedIfNeeded();
_results.push(id);
if (_results.size() >= numResults) {
// Once a plan returns enough results, stop working. Update cache with stats
// from this run and return.
updatePlanCache();
return Status::OK();
}
} else if (PlanStage::IS_EOF == state) {
// Cached plan hit EOF quickly enough. No need to replan. Update cache with stats
// from this run and return.
updatePlanCache();
return Status::OK();
} else if (PlanStage::NEED_YIELD == state) {
invariant(id == WorkingSet::INVALID_ID);
if (!yieldPolicy->canAutoYield()) {
throw WriteConflictException();
}
if (yieldPolicy->canAutoYield()) {
yieldPolicy->forceYield();
}
Status yieldStatus = tryYield(yieldPolicy);
if (!yieldStatus.isOK()) {
return yieldStatus;
}
} else if (PlanStage::FAILURE == state) {
// On failure, fall back to replanning the whole query. We neither evict the
// existing cache entry nor cache the result of replanning.
BSONObj statusObj;
WorkingSetCommon::getStatusMemberObject(*_ws, id, &statusObj);
LOG(1) << "Execution of cached plan failed, falling back to replan."
<< " query: " << redact(_canonicalQuery->toStringShort())
<< " planSummary: " << Explain::getPlanSummary(child().get())
<< " status: " << redact(statusObj);
const bool shouldCache = false;
return replan(yieldPolicy, shouldCache);
} else {
invariant(PlanStage::NEED_TIME == state);
}
}
// If we're here, the trial period took more than 'maxWorksBeforeReplan' work cycles. This
// plan is taking too long, so we replan from scratch.
LOG(1) << "Execution of cached plan required " << maxWorksBeforeReplan
<< " works, but was originally cached with only " << _decisionWorks
<< " works. Evicting cache entry and replanning query: "
<< redact(_canonicalQuery->toStringShort())
<< " plan summary before replan: " << Explain::getPlanSummary(child().get());
const bool shouldCache = true;
return replan(yieldPolicy, shouldCache);
}