I am witnessing a very bizzare behaviour of MongoDB.
I launch MongoD on a test system (Windows 10, 64bit) like this:
"C:\Program Files\MongoDB\Server\3.6\bin\mongod.exe" --dbpath "C:\MongoData"
I then shut down the server and replace the MongoData directory with a data set from a production server. I start mongod again, but I get a collection with 4 documents, which is what I used to have before I replaced my test data set with a real one.
That's not right, because I would expect to see loads of documents in a real data set. I then try dozens of things, including pointing MongoD to the data folder in its original location, which gives me all the documents from the real collection. Phew, the data is safe. But what is happening in my test system?
I have noticed that if I rename the folder in my test system to MongoData2 and lanuch mongod pointing at it then I get my proper production data set. but if I rename it back to MongoData and launch mongod pointing at this folder I get 4 documents again.
What is causing this?