implementing a database log

Hi,

i'm the author of a simple open-source database engine. i'm currently adding recovery/logging, and i have some practical questions about the implementation.

I have 3 options.

1. a physical log based on modified pages - whenever a page is modified, a before/after image is stored in the log. pro: easy to implement and to test con: logfile will become huge!
2. a physical log based on modified bytes - whenever a database key or record is modified, only the modified bytes in the file are logged. pro: logfile is slim, very fine-grained control con: tedious to implement, error prone, difficult to test
3. a logical logging - information about the high-level operation is stored in the logfile. honestly, i don't know how i could implement this, since one high-level operation is often splitted into several physical operations, and if one of them fails i am not sure about the consequences...

currently, i'm going with 2), but as i wrote above, it's hard to implement and i'm not happy with the way i'm going.

what would you recommend?

thanks for your opinions,
chris Received on Mon Apr 21 2008 - 14:44:52 CDT