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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/structure/record_store_v1_capped_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/structure/record_store_v1_capped.h"
namespace mongo {
//
// Capped collection traversal
//
CappedRecordStoreV1Iterator::CappedRecordStoreV1Iterator( OperationContext* txn,
const CappedRecordStoreV1* collection,
const DiskLoc& start, bool tailable,
const CollectionScanParams::Direction& dir)
: _txn(txn), _recordStore(collection), _curr(start), _tailable(tailable),
_direction(dir), _killedByInvalidate(false) {
if (_curr.isNull()) {
const RecordStoreV1MetaData* nsd = _recordStore->details();
// If a start position isn't specified, we fill one out from the start of the
// collection.
if (CollectionScanParams::FORWARD == _direction) {
// Going forwards.
if (!nsd->capLooped()) {
// If our capped collection doesn't loop around, the first record is easy.
_curr = collection->firstRecord(_txn);
}
else {
// Our capped collection has "looped' around.
// Copied verbatim from ForwardCappedCursor::init.
// TODO ELABORATE
_curr = _getExtent( nsd->capExtent() )->firstRecord;
if (!_curr.isNull() && _curr == nsd->capFirstNewRecord()) {
_curr = _getExtent( nsd->capExtent() )->lastRecord;
_curr = nextLoop(_curr);
}
}
}
else {
// Going backwards
if (!nsd->capLooped()) {
// Start at the end.
_curr = collection->lastRecord(_txn);
}
else {
_curr = _getExtent( nsd->capExtent() )->lastRecord;
}
}
}
}
bool CappedRecordStoreV1Iterator::isEOF() { return _curr.isNull(); }
DiskLoc CappedRecordStoreV1Iterator::curr() { return _curr; }
DiskLoc CappedRecordStoreV1Iterator::getNext() {
DiskLoc ret = _curr;
// Move to the next thing.
if (!isEOF()) {
_prev = _curr;
_curr = getNextCapped(_curr);
}
else if (_tailable && !_prev.isNull()) {
// If we're tailable, there COULD have been something inserted even though we were
// previously EOF. Look at the next thing from 'prev' and see.
DiskLoc newCurr = getNextCapped(_prev);
if (!newCurr.isNull()) {
// There's something new to return. _curr always points to the next thing to
// return. Update it, and move _prev to the thing we just returned.
_prev = ret = newCurr;
_curr = getNextCapped(_prev);
}
}
return ret;
}
void CappedRecordStoreV1Iterator::invalidate(const DiskLoc& dl) {
if ((_tailable && _curr.isNull() && dl == _prev) || (dl == _curr)) {
// In the _tailable case, we're about to kill the DiskLoc that we're tailing. Nothing
// that we can possibly do to survive that.
//
// In the _curr case, we *could* move to the next thing, since there is actually a next
// thing, but according to clientcursor.cpp:
// "note we cannot advance here. if this condition occurs, writes to the oplog
// have "caught" the reader. skipping ahead, the reader would miss postentially
// important data."
_curr = _prev = DiskLoc();
_killedByInvalidate = true;
}
}
void CappedRecordStoreV1Iterator::prepareToYield() {
}
bool CappedRecordStoreV1Iterator::recoverFromYield() {
// If invalidate invalidated the DiskLoc we relied on, give up now.
if (_killedByInvalidate) {
_recordStore = NULL;
return false;
}
return true;
}
DiskLoc CappedRecordStoreV1Iterator::getNextCapped(const DiskLoc& dl) {
invariant(!dl.isNull());
const RecordStoreV1MetaData* details = _recordStore->details();
if (CollectionScanParams::FORWARD == _direction) {
// If it's not looped, it's easy.
if (!_recordStore->details()->capLooped()) {
return _getNextRecord( dl );
}
// TODO ELABORATE
// EOF.
if (dl == _getExtent( details->capExtent() )->lastRecord) {
return DiskLoc();
}
DiskLoc ret = nextLoop(dl);
// If we become capFirstNewRecord from same extent, advance to next extent.
if (ret == details->capFirstNewRecord() && ret != _getExtent( details->capExtent() )->firstRecord) {
ret = nextLoop(_getExtent( details->capExtent() )->lastRecord);
}
// If we have just gotten to beginning of capExtent, skip to capFirstNewRecord
if (ret == _getExtent( details->capExtent() )->firstRecord) { ret = details->capFirstNewRecord(); }
return ret;
}
else {
if (!details->capLooped()) { return _getPrevRecord( dl ); }
// TODO ELABORATE
// Last record
if (details->capFirstNewRecord() == _getExtent( details->capExtent() )->firstRecord) {
if (dl == nextLoop(_getExtent( details->capExtent() )->lastRecord)) {
return DiskLoc();
}
}
else {
if (dl == _getExtent( details->capExtent() )->firstRecord) { return DiskLoc(); }
}
DiskLoc ret;
// If we are capFirstNewRecord, advance to prev extent, otherwise just get prev.
if (dl == details->capFirstNewRecord()) {
ret = prevLoop(_getExtent( details->capExtent() )->firstRecord);
}
else {
ret = prevLoop(dl);
}
// If we just became last in cap extent, advance past capFirstNewRecord
// (We know ext(capExtent)->firstRecord != capFirstNewRecord, since would
// have returned DiskLoc() earlier otherwise.)
if (ret == _getExtent( details->capExtent() )->lastRecord) {
ret = _getPrevRecord( details->capFirstNewRecord() );
}
return ret;
}
}
DiskLoc CappedRecordStoreV1Iterator::nextLoop(const DiskLoc& prev) {
// TODO ELABORATE
DiskLoc next = _getNextRecord( prev );
if (!next.isNull()) {
return next;
}
return _recordStore->firstRecord(_txn);
}
DiskLoc CappedRecordStoreV1Iterator::prevLoop(const DiskLoc& curr) {
// TODO ELABORATE
DiskLoc prev = _getPrevRecord( curr );
if (!prev.isNull()) {
return prev;
}
return _recordStore->lastRecord(_txn);
}
RecordData CappedRecordStoreV1Iterator::dataFor( const DiskLoc& loc ) const {
return _recordStore->dataFor( loc );
}
Extent* CappedRecordStoreV1Iterator::_getExtent( const DiskLoc& loc ) {
return _recordStore->_extentManager->getExtent( loc );
}
DiskLoc CappedRecordStoreV1Iterator::_getNextRecord( const DiskLoc& loc ) {
return _recordStore->getNextRecord( _txn, loc );
}
DiskLoc CappedRecordStoreV1Iterator::_getPrevRecord( const DiskLoc& loc ) {
return _recordStore->getPrevRecord( _txn, loc );
}
} // namespace mongo
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