From: Tom Lane <tgl@sss.pgh.pa.us>
To: Alvaro Herrera <alvherre@2ndquadrant.com>
cc: Michael Paquier <michael@paquier.xyz>,
        "Tsunakawa,
    Takayuki" <tsunakawa.takay@jp.fujitsu.com>,
        Robert Haas <robertmhaas@gmail.com>,
        PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: removal of dangling temp tables
In-reply-to: <201812281623.qlyp5nygu3pt@alvherre.pgsql>
References: <201812281623.qlyp5nygu3pt@alvherre.pgsql>
Comments: In-reply-to Alvaro Herrera <alvherre@2ndquadrant.com>
	message dated "Fri, 28 Dec 2018 13:23:58 -0300"
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Date: Fri, 28 Dec 2018 11:35:39 -0500
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Alvaro Herrera <alvherre@2ndquadrant.com> writes:
> On 2018-Dec-28, Alvaro Herrera wrote:
>> On 2018-Dec-28, Michael Paquier wrote:
>>> There are many exotic extensions which could be using sizeof(PGPROC)
>>> as that's a popular structure,

>> Can you show one instance of this?

> I looked at =

> https://github.com/postgrespro/pg_wait_sampling/blob/master/pg_wait_samp=
ling.c
> https://github.com/citusdata/citus/search?q=3Dpgproc&unscoped_q=3Dpgproc
> and skimmed a few others can't find any instance where the full struct
> is used, as opposed to just a pointer to it.

No, the point Michael is making is that the array stride in the ProcArray
is part of our ABI.  For example, accessing a PGPROC from its pgprocno
using the GetPGProcByNumber macro will be broken if we change the
struct size.  I do not think you can assume that no extension does that.

			regards, tom lane