Re: [HACKERS] Bug in prepared statement cache invalidation?

On Tue, May 2, 2017 at 5:50 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
>> Yeah.  I think there should be a way to tell a PL to flush any
>> internal caches it is maintaining, some variant of DISCARD.  But that
>> would require a bunch of code that nobody's written yet.
>
> That mechanism already exists, so far as the core code is concerned:
> register a syscache inval callback.  But you're right, getting plpgsql
> to actually do anything about changes in composite types would require
> a bunch of code that nobody's written yet.

Well, that'd be a way of doing automatic invalidations, not manual
ones.  Making DISCARD PROCEDURAL LANGUAGE CRAP work would a different
pile of code.

> If you'll pardon my bashing on a long-deceased horse, this would be
> noticeably easier if we stopped using the PLPGSQL_DTYPE_ROW code
> paths for composite-type variables.  That mechanism was really
> designed for cases like "SELECT ... INTO a,b,c" where the row
> contents are fully determined by the function text.  It's practically
> impossible to make it cope with dynamic changes; at the very least
> you have to recompile the whole function.

I guess that's also a project in need of some round tuits.

-- 
Robert Haas
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