Horton

Re: information_schema and not-null constraints

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Vik Fearing <vik@postgresfriends.org>
Cc: "David G. Johnston" <david.g.johnston@gmail.com>, Alvaro Herrera <alvherre@alvh.no-ip.org>, Pg Hackers <pgsql-hackers@lists.postgresql.org>, Peter Eisentraut <peter@eisentraut.org>, Peter Eisentraut <peter.eisentraut@enterprisedb.com>
Date: 2023-09-06T03:40:25Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Revert structural changes to not-null constraints

  2. Fix inconsistencies in error messages

  3. Disallow direct change of NO INHERIT of not-null constraints

  4. Disallow NO INHERIT not-null constraints on partitioned tables

  5. Better handle indirect constraint drops

  6. Don't try to assign smart names to constraints

  7. Fix restore of not-null constraints with inheritance

  8. ATTACH PARTITION: Don't match a PK with a UNIQUE constraint

  9. Fix propagating attnotnull in multiple inheritance

  10. Check stack depth in new recursive functions

  11. Move privilege check to the right place

  12. Update information_schema definition for not-null constraints

  13. Fix not-null constraint test

  14. Disallow changing NO INHERIT status of a not-null constraint

  15. Catalog not-null constraints

  16. parallel_schedule: add comment on event_trigger test dependency

  17. Revert "Catalog NOT NULL constraints" and fallout

  18. Adjust contrib/sepgsql regression test expected outputs.

  19. Fix table name clash in recently introduced test

  20. Catalog NOT NULL constraints

  21. Change the rules for inherited CHECK constraints to be essentially the same

Vik Fearing <vik@postgresfriends.org> writes:
> On 9/6/23 02:53, Tom Lane wrote:
>> What solution do you propose?  Starting to enforce the spec's rather
>> arbitrary requirement that constraint names be unique per-schema is
>> a complete nonstarter.  Changing the set of columns in a spec-defined
>> view is also a nonstarter, or at least we've always taken it as such.

> I both semi-agree and semi-disagree that these are nonstarters.  One of 
> them has to give.

[ shrug... ] if you stick to a SQL-compliant schema setup, then the
information_schema views will serve for introspection.  If you don't,
they won't, and you'll need to look at Postgres-specific catalog data.
This compromise has served for twenty years or so, and I'm not in a
hurry to change it.  I think the odds of changing to the spec's
restriction without enormous pushback are nil, and I do not think
that the benefit could possibly be worth the ensuing pain to users.
(It's not even the absolute pain level that is a problem, so much
as the asymmetry: the pain would fall exclusively on users who get
no benefit, because they weren't relying on these views anyway.
If you think that's an easy sell, you're mistaken.)

It could possibly be a little more palatable to add column(s) to the
information_schema views, but I'm having a hard time seeing how that
moves the needle.  The situation would still be precisely describable
as "if you stick to a SQL-compliant schema setup, then the standard
columns of the information_schema views will serve for introspection.
If you don't, they won't, and you'll need to look at Postgres-specific
columns".  That doesn't seem like a big improvement.  Also, given your
point about normalization, how would we define the additions exactly?

			regards, tom lane