Re: truncating pg_multixact/members

On 2014-02-12 17:40:44 -0300, Alvaro Herrera wrote:
> > > Also, AutoVacOpts (used as part of reloptions) gained three extra
> > > fields. Since this is in the middle of StdRdOptions, it'd be somewhat
> > > more involve to put these at the end of that struct. This might be a
> > > problem if somebody has a module calling RelationIsSecurityView(). If
> > > anyone thinks we should be concerned about such an ABI change, please
> > > shout quickly.
> >
> > That sounds problematic --- surely StdRdOptions might be something
> > extensions are making use of?
>
> So can we assume that security_barrier is the only thing to be concerned
> about? If so, the attached patch should work around the issue by
> placing it in the same physical location.

Aw. How instead about temporarily introducing AutoVacMXactOpts or
something? Changing the name of the member variable sounds just as
likely to break things.

> I guess if there are modules
> that add extra stuff beyond StdRdOptions, this wouldn't work, but I'm
> not really sure how likely this is given that our reloptions design
> hasn't proven to be the most extensible thing in the world.

Hm, I don't see how it'd be problematic, even if they do. I don't really
understand the design of the reloptions code, but afaics, they shouldn't
do so by casting around rd_options but by parsing it anew, right?

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
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