Re: Cache lookup errors with functions manipulation object addresses

From: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
To: Michael Paquier <michael(at)paquier(dot)xyz>
Cc: Andrew Dunstan <andrew(dot)dunstan(at)2ndquadrant(dot)com>, pgsql-hackers(at)lists(dot)postgresql(dot)org
Subject: Re: Cache lookup errors with functions manipulation object addresses
Date: 2018-12-13 17:58:02
Message-ID: 20181213175802.pz75lgq3rhgbdzwz@alvherre.pgsql
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On 2018-Dec-13, Michael Paquier wrote:

> > I support 0001 other than those two points.
>
> Attached is an updated version for that as 0001. Thanks for the
> review. Does that part look good to you now?

+1.

> > +SELECT * FROM pg_identify_object_as_address('pg_proc'::regclass, 0, 0); -- no function
> > + type | object_names | object_args
> > +------+--------------+-------------
> > + | {} | {}
> > +(1 row)
> >
> > All the other cases you add have a non-empty value in "type".
>
> On this one I would expect NULL for object_names and object_args, as
> empty does not make sense for an undefined object, still "type" should
> print... "type".

Hmm ... "routine"?

I'm not sure if NULLs are better than empty arrays, but I agree that we
should pick one representation for undefined object and use it
consistently for all object types.

> > I think this is our chance to fix the mess. Previously (before I added
> > the SQL-access of the object addressing mechanism in 9.5 I mean) it
> > wasn't possible to get at this code at all with arbitrary input, so this
> > is all a "new" problem (I mean new in the last 5 years).

Obviously I failed to subtract 11 from 9.5 correctly ... I meant 4
years.

> This requires a bit more work with the low-level APIs grabbing the
> printed information though. And I think that the following guidelines
> make sense to work on as a base definition for undefined objects:
> - pg_identify_object returns the object type name, NULL for the other fields.
> - pg_describe_object returns just NULL.
> - pg_identify_object_as_address returns the object type name and NULL
> for the other fields.

Sounds good to me.

> There is some more refactoring work still needed for constraints, large
> objects and functions, in a way similar to a26116c6. I am pretty happy
> with the shape of 0001, so this could be applied, 0002 still needs to be
> reworked so as all undefined object types behave as described above in a
> consistent manner. Do those definitions make sense?

I think so, yes.

Thanks for taking care of this.

--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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