Re: pgsql: Fix crash bug in RestoreSnapshot.

On Fri, Jul 1, 2016 at 10:43 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Simon Riggs <simon@2ndquadrant.com> writes:
>> On 1 July 2016 at 16:04, Robert Haas <robertmhaas@gmail.com> wrote:
>>> Because that's where the code was added.  In 9.5, it would only matter
>>> for extensions using the ParallelContext machinery.
>
>> It seems strange to me to make an unnecessary change to a production
>> release, that's all.
>> My understanding was that we backpatched only as far as a bug occurs,
>> rather than as far as patch can be applied.
>
> I think Robert is saying that the problem *is* reachable in 9.5, given
> a suitable extension.  In that case fixing it is appropriate, whether
> or not we know of such an extension today.

Right.  This is no different from any of the other fixes for parallel
infrastructure which have been back-patched to the releases in which
the relevant code was added - in particular, see commits
038aa89af53ee6ee26dfc9e73704d4e94701588f,
5eca6cf99411bfd47f43fc742552c9a2ae459bc8,
87abcb4ebd48f5d8f7244236f8839854c1861537,
e9215461d2a6081812d9c3619c9ec81e5682fe0f,
e72f2115ef6d574c64f42ea8b4cbe96accee08b2,
df58a17df29f7ec0ffc8389deee46e81a2a58a60,
c98605cc47fe42fac5f685d611db2a0c1afa2fcf,
73d71cde5751e06d372431178e740835284eb132,
14129d1c9e2d3afa064651012a55c9c84aa6821a,
26981d292758c6ee9185332e4abc990ff19c81a2, and
91d97f03ca2a9ed56b322b69dde0392db835f722.  There are probably others.
I think it's our standard practice to back-patch bug fixes to the
point at which the code was introduced, even if in that release the
code can only be reached by an extension.  I can't actually understand
why we would do anything else.  There's no benefit to leaving that
code broken in 9.5.

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