Re: More stable query plans via more predictable column statistics

On Thu, Mar 3, 2016 at 2:48 AM, Shulgin, Oleksandr
<oleksandr.shulgin@zalando.de> wrote:
> On Wed, Mar 2, 2016 at 7:33 PM, Alvaro Herrera <alvherre@2ndquadrant.com>
> wrote:
>> Shulgin, Oleksandr wrote:
>>
>> > Alright.  I'm attaching the latest version of this patch split in two
>> > parts: the first one is NULLs-related bugfix and the second is the
>> > "improvement" part, which applies on top of the first one.
>>
>> So is this null-related bugfix supposed to be backpatched?  (I assume
>> it's not because it's very likely to change existing plans).
>
> For the good, because cardinality estimations will be more accurate in these
> cases, so yes I would expect it to be back-patchable.

-1.  I think the cost of changing existing query plans in back
branches is too high.  The people who get a better plan never thank
us, but the people who (by bad luck) get a worse plan always complain.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company