Issue with _p_mtime when mocking time with python-libfaketime about persistent HOT 4 CLOSED

_p_mtime is just a wrapper (which loses precision, by the way) around _p_serial. In ZODB, _p_serial is the transaction ID, and transaction IDs always increase; they can never go backwards. When you create the DB, ZODB creates the first transaction to initially create the root object, and thus establishes the baseline for all transaction IDs going forward.

>>> db = ZODB.DB(None)
>>> db._storage.lastTransaction()
b'\x03\xd1\xffFF\xd1+\x00'
>>> db.open().root()._p_serial
b'\x03\xd1\xffFF\xd1+\x00'

When it's time to commit, ZODB essentially says to the TimeStamp class, "give me a TimeStamp based on the current time that's later than the last one I committed." If the clock has gone backwards, it'll be ignored.

from persistent.

@jamadden Thank you for your excellent explanation.
@azmeuk Does this explanation answer your question so the issue can be closed?

from persistent.

from persistent.

@jamadden Thank you. Your answer helped me a lot understand what is going on.
@icemac Yep!

from persistent.