Re: proposal: get oldest LSN - function

On Sun, Feb 28, 2016 at 4:40 PM, Kartyshov Ivan wrote:
> It will not satisfy our purposes and our administrators for three reasons.
> 1) DBA set me task to get the oldest number that present in WAL, not last

Yeah I got that.

> 2) Surely we can choose the oldest segment from list "pg_ls_dir('pg_xlog')"
> of segments and calculate the first LSN by hand, but it is not what we want
> to do manually.

That's where I am not following. In any case you are just one SQL
query away from the result. And actually your patch is incorrect I
think. If you care about the oldest record available you should look
for the first LSN position of the oldest segment, no? What you are
calculating now is the oldest virtual LSN position in local pg_xlog.
--
Michael