Re: [HACKERS] Possible TODO: allow arbitrary expressions in eventtrigger WHEN

On Mon, Feb 13, 2017 at 10:34 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Jim Nasby <Jim.Nasby@BlueTreble.com> writes:
>> Is there a reason not to allow $SUBJECT? Specifically, it'd be nice to
>> be able to do something like WHEN tag LIKE 'ALTER%'.
>
> Seems like it would be a seriously bad idea for such an expression to be
> able to invoke arbitrary SQL code.  What if it calls a user-defined
> function that tries to do DDL?

Yeah.  I remember thinking about this and deciding that allowing real
expressions there was totally intractable.  I don't remember what all
the reasons were, but what Tom's talking about may have been at least
part of it.

-- 
Robert Haas
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