Horton

Re: [HACKERS] [BUGS] BUG #14825: enum type: unsafe use?

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Thomas Munro <thomas.munro@enterprisedb.com>, Andrew Dunstan <andrew.dunstan@2ndquadrant.com>, Tom Lane <tgl@sss.pgh.pa.us>, Stephen Frost <sfrost@snowman.net>, Bruce Momjian <bruce@momjian.us>, "David E. Wheeler" <david@justatheory.com>, Christophe Pettus <christophe.pettus@pgexperts.com>, Postgres-Bugs <pgsql-bugs@postgresql.org>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2018-01-12T22:06:12Z
Lists: pgsql-bugs, pgsql-hackers 
On 2018-01-12 07:51:34 -0500, Robert Haas wrote:
> On Thu, Jan 11, 2018 at 11:01 PM, Thomas Munro
> <thomas.munro@enterprisedb.com> wrote:
> > Are you saying we should do the work now to create a per-transaction
> > DSM segment + DSA area + thing that every backend attaches to?
> 
> No, I was just thinking you could stuff it into the per-parallel-query
> DSM/DSA.  But...
> 
> > I didn't think creating backend local hash tables would be a problem
> > because it's a vanishingly rare occurrence for the hash table to be
> > created at all (ie when you've altered an enum), and if created, to
> > have more than a couple of entries in it.
> 
> ...this is also a fair point.

OTOH, it seems quite likely that we'll add more transaction-lifetime
shared data (e.g. combocid), so building per-xact infrastructure
actually seems like a good idea.

Greetings,

Andres Freund

Commits

  1. Revert to 9.6 treatment of ALTER TYPE enumtype ADD VALUE.

  2. Remove heuristic same-transaction test from check_safe_enum_use().

  3. Use a blacklist to distinguish original from add-on enum values.

  4. Add support for coordinating record typmods among parallel workers.