Re: Avoiding pin scan during btree vacuum - Mailing list pgsql-hackers

From Robert Haas
Subject Re: Avoiding pin scan during btree vacuum
Date
Msg-id CA+Tgmob_Osj8N+BfMPDh4gD_SKveRp+_Xu_1MqNiBGdUZCBxMQ@mail.gmail.com
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In response to Re: Avoiding pin scan during btree vacuum  (Alvaro Herrera <alvherre@2ndquadrant.com>)
Responses Re: Avoiding pin scan during btree vacuum  (Alvaro Herrera <alvherre@2ndquadrant.com>)
List pgsql-hackers
On Wed, Oct 19, 2016 at 6:30 PM, Alvaro Herrera
<alvherre@2ndquadrant.com> wrote:
> Robert Haas wrote:
>> On Mon, Jan 4, 2016 at 10:30 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> >> This seems like a might subtle thing to backpatch. If we really want to
>> >> go there, ISTM that the relevant code should stew in an unreleased
>> >> branch for a while, before being backpatched.
>> >
>> > I'm definitely -1 on back-patching such a thing.  Put it in HEAD for
>> > awhile.  If it survives six months or so then we could discuss it again.
>>
>> I agree with Tom.
>
> Okay, several months have passed with this in the development branch and
> now seems a good time to backpatch this all the way back to 9.4.
>
> Any objections?

Although the code has now been in the tree for six months, it's only
been in a released branch for three weeks, which is something about
which to think.

I guess what's really bothering me is that I don't think this is a bug
fix.  It seems like a performance optimization.  And I think that we
generally have a policy that we don't back-patch performance
optimizations.  Of course, there is some fuzziness because when the
performance gets sufficiently bad, we sometimes decide that it amounts
to a bug, as in 73cc7d3b240e1d46b1996382e5735a820f8bc3f7.  Maybe this
case qualifies for similar treatment, but I'm not sure.

Why are you talking about back-patching this to 9.4 rather than all
supported branches?

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



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