Re: pg_controldata/pg_resetxlog "Latest checkpoint's NextXID" format

On 30 December 2015 at 00:17, Joe Conway <mail(at)joeconway(dot)com> wrote:

> On 12/29/2015 07:15 AM, Tom Lane wrote:
> > Yeah. Use of the same x/y notation with two different bases seems like
> > a recipe for confusion. It's probably too late to do anything about
> > this for 9.5, but I'd be +1 for adopting Jose's suggestion or some
> > other formatting tweak in HEAD.
>
> I made the "%u/%u" -> "%u:%u" change in the controldata patch I just
> posted, but I suppose I should commit that separately. Any complaints
> about that?

There is already long precedent about how to represent an XID with an
epoch... and it is neither of those two formats.

http://www.postgresql.org/docs/devel/static/functions-info.html
"Table 9-63. Transaction IDs and Snapshots"
"The internal transaction ID type (xid) is 32 bits wide and wraps around
every 4 billion transactions. However, these functions export a 64-bit
format that is extended with an "epoch" counter so it will not wrap around
during the life of an installation."

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