On 2 February 2013 00:24, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> * The return value is also adjusted with vacuum_defer_cleanup_age, so
> * increasing that setting on the fly is another easy way to make
> * GetOldestXmin() move backwards, with no consequences for data integrity.
>
> And as for that, it's been pretty clear for awhile that allowing
> vacuum_defer_cleanup_age to change on the fly was a bad idea we'd
> eventually have to undo. The day of reckoning has arrived: it needs
> to be PGC_POSTMASTER.
Agreed, will fix.
-- Simon Riggs http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training & Services