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/**
* Copyright (C) 2013 10gen Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* 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
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* 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 GNU Affero General 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.
*/
#include "mongo/platform/basic.h"
#include "mongo/db/exec/count.h"
#include "mongo/db/catalog/collection.h"
#include "mongo/db/exec/scoped_timer.h"
#include "mongo/db/exec/working_set_common.h"
namespace mongo {
// static
const char* CountStage::kStageType = "COUNT";
CountStage::CountStage(OperationContext* txn,
Collection* collection,
const CountRequest& request,
WorkingSet* ws,
PlanStage* child)
: _txn(txn),
_collection(collection),
_request(request),
_leftToSkip(request.skip),
_ws(ws),
_child(child),
_commonStats(kStageType) { }
CountStage::~CountStage() { }
bool CountStage::isEOF() {
if (_specificStats.trivialCount) {
return true;
}
if (_request.limit > 0 && _specificStats.nCounted >= _request.limit) {
return true;
}
return NULL != _child.get() && _child->isEOF();
}
void CountStage::trivialCount() {
invariant(_collection);
long long nCounted = _collection->numRecords(_txn);
if (0 != _request.skip) {
nCounted -= _request.skip;
if (nCounted < 0) {
nCounted = 0;
}
}
long long limit = _request.limit;
if (limit < 0) {
limit = -limit;
}
if (limit < nCounted && 0 != limit) {
nCounted = limit;
}
_specificStats.nCounted = nCounted;
_specificStats.nSkipped = _request.skip;
_specificStats.trivialCount = true;
}
PlanStage::StageState CountStage::work(WorkingSetID* out) {
++_commonStats.works;
// Adds the amount of time taken by work() to executionTimeMillis.
ScopedTimer timer(&_commonStats.executionTimeMillis);
// This stage never returns a working set member.
*out = WorkingSet::INVALID_ID;
// If we don't have a query and we have a non-NULL collection, then we can execute this
// as a trivial count (just ask the collection for how many records it has).
if (_request.query.isEmpty() && NULL != _collection) {
trivialCount();
return PlanStage::IS_EOF;
}
if (isEOF()) {
_commonStats.isEOF = true;
return PlanStage::IS_EOF;
}
// For non-trivial counts, we should always have a child stage from which we can retrieve
// results.
invariant(_child.get());
WorkingSetID id = WorkingSet::INVALID_ID;
PlanStage::StageState state = _child->work(&id);
if (PlanStage::IS_EOF == state) {
_commonStats.isEOF = true;
return PlanStage::IS_EOF;
}
else if (PlanStage::DEAD == state) {
return state;
}
else if (PlanStage::FAILURE == state) {
*out = id;
// If a stage fails, it may create a status WSM to indicate why it failed, in which cas
// 'id' is valid. If ID is invalid, we create our own error message.
if (WorkingSet::INVALID_ID == id) {
const std::string errmsg = "count stage failed to read result from child";
Status status = Status(ErrorCodes::InternalError, errmsg);
*out = WorkingSetCommon::allocateStatusMember(_ws, status);
}
return state;
}
else if (PlanStage::ADVANCED == state) {
// We got a result. If we're still skipping, then decrement the number left to skip.
// Otherwise increment the count until we hit the limit.
if (_leftToSkip > 0) {
_leftToSkip--;
_specificStats.nSkipped++;
}
else {
_specificStats.nCounted++;
}
// Count doesn't need the actual results, so we just discard any valid working
// set members that got returned from the child.
if (WorkingSet::INVALID_ID != id) {
_ws->free(id);
}
}
else if (PlanStage::NEED_FETCH == state) {
*out = id;
_commonStats.needFetch++;
return PlanStage::NEED_FETCH;
}
_commonStats.needTime++;
return PlanStage::NEED_TIME;
}
void CountStage::saveState() {
_txn = NULL;
++_commonStats.yields;
if (_child.get()) {
_child->saveState();
}
}
void CountStage::restoreState(OperationContext* opCtx) {
invariant(_txn == NULL);
_txn = opCtx;
++_commonStats.unyields;
if (_child.get()) {
_child->restoreState(opCtx);
}
}
void CountStage::invalidate(OperationContext* txn, const DiskLoc& dl, InvalidationType type) {
++_commonStats.invalidates;
if (_child.get()) {
_child->invalidate(txn, dl, type);
}
}
vector<PlanStage*> CountStage::getChildren() const {
vector<PlanStage*> children;
if (_child.get()) {
children.push_back(_child.get());
}
return children;
}
PlanStageStats* CountStage::getStats() {
_commonStats.isEOF = isEOF();
auto_ptr<PlanStageStats> ret(new PlanStageStats(_commonStats, STAGE_COUNT));
CountStats* countStats = new CountStats(_specificStats);
ret->specific.reset(countStats);
if (_child.get()) {
ret->children.push_back(_child->getStats());
}
return ret.release();
}
const CommonStats* CountStage::getCommonStats() {
return &_commonStats;
}
const SpecificStats* CountStage::getSpecificStats() {
return &_specificStats;
}
} // namespace mongo
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