On 2/3/2007 4:05 PM, Theo Schlossnagle wrote:
On Feb 3, 2007, at 3:52 PM, Jan Wieck wrote:
On 2/1/2007 11:23 PM, Jim Nasby wrote:
On Jan 25, 2007, at 6:16 PM, Jan Wieck wrote:
If a per database configurable tslog_priority is given, the
timestamp will be truncated to milliseconds and the increment
logic is done on milliseconds. The priority is added to the
timestamp. This guarantees that no two timestamps for commits
will ever be exactly identical, even across different servers.
Wouldn't it be better to just store that information separately,
rather than mucking with the timestamp?
Though, there's anothe issue here... I don't think NTP is good
for any better than a few milliseconds, even on a local network.
How exact does the conflict resolution need to be, anyway? Would
it really be a problem if transaction B committed 0.1 seconds
after transaction A yet the cluster thought it was the other way
around?
Since the timestamp is basically a Lamport counter which is just
bumped be the clock as well, it doesn't need to be too precise.
Unless I'm missing something, you are _treating_ the counter as a
Lamport timestamp, when in fact it is not and thus does not provide
semantics of a Lamport timestamp. As such, any algorithms that use
lamport timestamps as a basis or assumption for the proof of their
correctness will not translate (provably) to this system.
How are your counter semantically equivalent to Lamport timestamps?
Yes, you must be missing something.
The last used timestamp is remembered. When a remote transaction is
replicated, the remembered timestamp is set to max(remembered, remote).
For a local transaction, the remembered timestamp is set to
max(remembered+1ms, systemclock) and that value is used as the
transaction commit timestamp.
Jan
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