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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,
const DiskLoc& start,
const CollectionScanParams::Direction& dir)
: _txn(txn), _curr(start), _recordStore(collection), _direction(dir) {
if (_curr.isNull()) {
const ExtentManager* em = _recordStore->_extentManager;
if ( _recordStore->details()->firstExtent(txn).isNull() ) {
// nothing in the collection
verify( _recordStore->details()->lastExtent(txn).isNull() );
}
else if (CollectionScanParams::FORWARD == _direction) {
// 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;
}
}
}
bool SimpleRecordStoreV1Iterator::isEOF() {
return _curr.isNull();
}
DiskLoc SimpleRecordStoreV1Iterator::curr() { return _curr; }
DiskLoc SimpleRecordStoreV1Iterator::getNext() {
DiskLoc ret = _curr;
// Move to the next thing.
if (!isEOF()) {
if (CollectionScanParams::FORWARD == _direction) {
_curr = _recordStore->getNextRecord( _txn, _curr );
}
else {
_curr = _recordStore->getPrevRecord( _txn, _curr );
}
}
return ret;
}
void SimpleRecordStoreV1Iterator::invalidate(const DiskLoc& dl) {
// Just move past the thing being deleted.
if (dl == _curr) {
// We don't care about the return of getNext so much as the side effect of moving _curr
// to the 'next' thing.
getNext();
}
}
void SimpleRecordStoreV1Iterator::prepareToYield() {
}
bool SimpleRecordStoreV1Iterator::recoverFromYield() {
// if the collection is dropped, then the cursor should be destroyed
return true;
}
RecordData SimpleRecordStoreV1Iterator::dataFor( const DiskLoc& loc ) const {
return _recordStore->dataFor( loc );
}
}
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