encrypted database to be re-encrypted with a new password.
Here are some ideas for an initial implementation.
The easiest way to do this is to make sure we have exclusive access to the
data and that no log is required in the new copy of the db. I want to avoid
the log as it also is encrypted. Here is my VERY high level plan:
1) Force exclusive access by putting all the work in the low level store,
offline boot method. We will do redo recovery as usual, but at the end
there will be an entry point to do the copy/encrypt operation.
0) The request to encrypt/re-encrypt the db will be handled with a new set
of url flags passed into store at boot time. The new flags will provide
the same inputs as the current encrypt flags. So at high level the
request will be "connect db old_encrypt_url_flags; new_encrypt_url_flags".
TODO - provide exact new flag syntax.
1) Open a transaction do all logged work to do the encryption. All logging
will be done with existing encryption.
2) Copy and encrypt every db file in the database. The target files will
be in the data directory. There will be a new suffix to track the new
files, similar to the current process used for handling drop table in
a transaction consistent manner without logging the entire table to the log.
Entire encrypted destination file is guaranteed synced to disk before
transaction commits. I don't think this part needs to be logged.
Files will be read from the cache using existing mechanism and written
directly into new encrypted files (new encrypted data does not end up in
3) Switch encrypted files for old files. Do this under a new log operation
so the process can be correctly rolled back if the encrypt db operation
transaction fails. Rollback will do file at a time switches, no reading
of encrypted data is necessary.
4) log a "change encryption of db" log record, but do not update
system.properties with the change.
5) commit transaction.
6) update system.properties and sync changes.
7) TODO - need someway to handle crash between steps 5 and 6.
6) checkpoint all data, at this point guaranteed that there is no outstanding
transaction, so after checkpoint is done there is no need for the log.
o there probably should be something that catches a request to encrypt to
whatever db was already encrypted with.