Re: tracking commit timestamps

On Sun, 2014-11-09 at 11:57 -0500, Steve Singer wrote:

> The reason why Jim and myself are asking for the LSN and not just the 
> timestamp is that I want to be able to order the transactions. Jim 
> pointed out earlier in the thread that just ordering on timestamp allows 
> for multiple transactions with the same timestamp.
> 
> Maybe we don't need the entire LSN to solve that.  If you already have 
> the commit timestamp maybe you only need another byte or two of 
> granularity to order transactions that are within the same microsecond.

There is no guarantee that a commit with later LSN has a later
timestamp. There are cases where the clock could move significantly
backwards.

A robust solution to storing transaction commit information (including
commit order) in a way that can be referenced from other tables, can be
loaded to another cluster, and survives crashes would be a great
feature. But this feature doesn't have those properties.
- Anssi