| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | "Shulgin, Oleksandr" <oleksandr(dot)shulgin(at)zalando(dot)de> |
| Cc: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, David Steele <david(at)pgmasters(dot)net>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: More stable query plans via more predictable column statistics |
| Date: | 2016-03-04 18:27:35 |
| Message-ID: | CA+TgmoZrcTZPJEaSHriSbEsJkB7pO=46fXoKVK1bQY6=KLqZsQ@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Thu, Mar 3, 2016 at 2:48 AM, Shulgin, Oleksandr
<oleksandr(dot)shulgin(at)zalando(dot)de> wrote:
> On Wed, Mar 2, 2016 at 7:33 PM, Alvaro Herrera <alvherre(at)2ndquadrant(dot)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
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