OplogReader syncSourceReader; OpTime minValid; if (_replCoord->getMemberState().recovering()) { BatchBoundaries boundaries = getMinValid(txn); if (boundaries.end > lastOpTimeFetched) { minValid = boundaries.end; } } syncSourceReader.connectToSyncSource(txn, lastOpTimeFetched, minValid, _replCoord); connectToSyncSource wil use db.oplog.rs.find( ts: {$gte: minValid, $lte: minvalid}) to check this oplog in sync source, which will trigger oplogStartHack. When the minvalid optime exists in sync source, the oplogStartHack work very well; but if it doesn't exists in sync source, it will cause oplog full table scan. I think when the minvaid doesn't exist in sync source, RecordStore::oplogStartHack should return RecordId::max() to avoid full oplog table scan, which is a very heavy operation. diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_record_store.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_record_store.cpp index f6fa6d6..94a1d48 100644 --- a/src/mongo/db/storage/wiredtiger/wiredtiger_record_store.cpp +++ b/src/mongo/db/storage/wiredtiger/wiredtiger_record_store.cpp @@ -1792,7 +1792,7 @@ boost::optional<RecordId> WiredTigerRecordStore::oplogStartHack( if (ret == 0 && cmp > 0) ret = c->prev(c); // landed one higher than startingPosition if (ret == WT_NOTFOUND) - return RecordId(); // nothing <= startingPosition + return RecordId::max(); // will not cause oplog full scan invariantWTOK(ret); int64_t key;