On 08/19/2015 01:32 PM, Tom Lane wrote: > Josh Berkus <j...@agliodbs.com> writes: >> On 08/18/2015 04:40 PM, Qingqing Zhou wrote: >>> Attached please find the WIP patch and also the ANALYZE results. >>> Notes: the patch may not directly apply to head as some network issue >>> here so my Linux box can't talk to git server. > >> So, one of the things we previously mentioned is that currently many >> users deliberately use CTEs as an optimization barrier in order to force >> the planner. Given that, we need some kind of option to force the old >> behavior; either SQL syntax or a GUC option. > > I think we already agreed what the syntax would be: ye good olde OFFSET 0 > in the subquery. > > We could have a GUC option too if people are sufficiently worried about > it, but I think that the need for one hasn't really been proven.
Asking users to refactor their applications to add OFFSET 0 is a bit painful, if we could take care of it via a backwards-compatibility GUC. We have many users who are specifically using the CTE optimization barrier to work around planner failures. -- Josh Berkus PostgreSQL Experts Inc. http://pgexperts.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
