Re: Making clausesel.c Smarter

On 2/26/17 1:41 AM, Robert Haas wrote:
> On Fri, Feb 24, 2017 at 3:30 PM, David Rowley
> <david(dot)rowley(at)2ndquadrant(dot)com> wrote:
>> It would be good to improve the situation here in the back branches
>> too, but I'm thinking that the attached might be a little invasive for
>> that?
>
> My experience has been that customers - at least EnterpriseDB
> customers - do not appreciate plan changes when they upgrade to a new
> minor release. Most people have production installations that are
> basically working; if not, they wouldn't be in production. Even if
> they're getting a good plan only by some happy accident, they're still
> getting it, and a change can cause a good plan to flop over into a bad
> plan, which can easily turn into a service outage. The people who had
> a bad plan and get flipped to a good plan will be happy once they
> realize what has changed, of course, but that's not really enough to
> make up from the panicked calls from customers whose stuff falls over
> when they try to apply the critical security update.
>
> I think the basic think you are trying to accomplish is sensible,
> though. I haven't reviewed the patch.

This patch applies cleanly and compiles at cccbdde. I agree with Robert
that back patching would likely not be a good idea.

Anyone familiar with the planner available to review this patch?

It also seems like this would be a (relatively) simple patch to start
with for anyone that is interested in learning more about the planner.

--
-David
david(at)pgmasters(dot)net