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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/db/storage/mmap_v1/record_store_v1_simple_iterator.h"
#include "mongo/db/catalog/collection.h"
#include "mongo/db/storage/mmap_v1/extent.h"
#include "mongo/db/storage/mmap_v1/extent_manager.h"
#include "mongo/db/storage/mmap_v1/record_store_v1_simple.h"
namespace mongo {
//
// Regular / non-capped collection traversal
//
SimpleRecordStoreV1Iterator::SimpleRecordStoreV1Iterator(OperationContext* txn,
const SimpleRecordStoreV1* collection,
bool forward)
: _txn(txn), _recordStore(collection), _forward(forward) {
// Eagerly seek to first Record on creation since it is cheap.
const ExtentManager* em = _recordStore->_extentManager;
if (_recordStore->details()->firstExtent(txn).isNull()) {
// nothing in the collection
verify(_recordStore->details()->lastExtent(txn).isNull());
} else if (_forward) {
// Find a non-empty extent and start with the first record in it.
Extent* e = em->getExtent(_recordStore->details()->firstExtent(txn));
while (e->firstRecord.isNull() && !e->xnext.isNull()) {
e = em->getExtent(e->xnext);
}
// _curr may be set to DiskLoc() here if e->lastRecord isNull but there is no
// valid e->xnext
_curr = e->firstRecord;
} else {
// Walk backwards, skipping empty extents, and use the last record in the first
// non-empty extent we see.
Extent* e = em->getExtent(_recordStore->details()->lastExtent(txn));
// TODO ELABORATE
// Does one of e->lastRecord.isNull(), e.firstRecord.isNull() imply the other?
while (e->lastRecord.isNull() && !e->xprev.isNull()) {
e = em->getExtent(e->xprev);
}
// _curr may be set to DiskLoc() here if e->lastRecord isNull but there is no
// valid e->xprev
_curr = e->lastRecord;
}
}
boost::optional<Record> SimpleRecordStoreV1Iterator::next() {
if (isEOF())
return {};
auto toReturn = _curr.toRecordId();
advance();
return {{toReturn, _recordStore->RecordStore::dataFor(_txn, toReturn)}};
}
boost::optional<Record> SimpleRecordStoreV1Iterator::seekExact(const RecordId& id) {
_curr = DiskLoc::fromRecordId(id);
advance();
return {{id, _recordStore->RecordStore::dataFor(_txn, id)}};
}
void SimpleRecordStoreV1Iterator::advance() {
// Move to the next thing.
if (!isEOF()) {
if (_forward) {
_curr = _recordStore->getNextRecord(_txn, _curr);
} else {
_curr = _recordStore->getPrevRecord(_txn, _curr);
}
}
}
void SimpleRecordStoreV1Iterator::invalidate(OperationContext* txn, const RecordId& dl) {
// Just move past the thing being deleted.
if (dl == _curr.toRecordId()) {
const DiskLoc origLoc = _curr;
// Undo the advance on rollback, as the deletion that forced it "never happened".
txn->recoveryUnit()->onRollback([this, origLoc]() { this->_curr = origLoc; });
advance();
}
}
void SimpleRecordStoreV1Iterator::save() {}
bool SimpleRecordStoreV1Iterator::restore() {
// if the collection is dropped, then the cursor should be destroyed
return true;
}
std::unique_ptr<RecordFetcher> SimpleRecordStoreV1Iterator::fetcherForNext() const {
return _recordStore->_extentManager->recordNeedsFetch(_curr);
}
std::unique_ptr<RecordFetcher> SimpleRecordStoreV1Iterator::fetcherForId(const RecordId& id) const {
return _recordStore->_extentManager->recordNeedsFetch(DiskLoc::fromRecordId(id));
}
}
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