Re: Disallow unique index on system columns

On Sat, Apr 16, 2016 at 12:14 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

>
> Pushed. I moved the check into DefineIndex, as that's where user-facing
> complaints about indexes generally ought to be.
>

If you're planning on back-patching this, please don't. :) It'll
literally ruin my life.

I've got an extension that's actually a custom Access Method, and for
reasons that are probably too boring to go into here, it requires that the
first column in the index be a function that takes the ctid. Ie, something
akin to:

CREATE INDEX idx ON table (my_func('table', ctid), other_func(table));

The AM implementation itself doesn't actually use the result of my_func(),
but that construct is necessary so I can detect certain queries that look
like:
SELECT FROM table WHERE my_func('table', ctid) ==> 'index condition'

I don't mind that you're changing this for 9.6... 9.6 is going to change so
much other stuff around custom AMs that I'll deal with it when the time
comes, but back-patching this into 9.3/4/5 would make life very difficult.

Thanks for listening!

eric