On 28 February 2017 at 13:05, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Alvaro Herrera <alvherre@2ndquadrant.com> writes:
>> This patch reduces the amount of bloat you get from running CREATE INDEX
>> CONCURRENTLY by destroying the snapshot taken in the first phase, before
>> entering the second phase. This allows the global xmin to advance,
>
> Um ... isn't there a transaction boundary there anyway?
Yes, the patch releases the snapshot early, so it does not hold it
once the build scan has completed. This allows the sort and build
phases to occur without holding back the xmin.
--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services