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Re: Proposed patch for sequence-renaming problems

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-patches(at)postgresql(dot)org
Subject: Re: Proposed patch for sequence-renaming problems
Date: 2005-09-27 23:44:20
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackerspgsql-patches
I looked over the patch, and while it does fix the problem for SERIAL, I
am concerned about expecting users to user ::regclass in normal usage,
and I am concerned about adding something we will have to support in the
future when we come up with a better solution.  Why is regclass not
being used automatically?


Tom Lane wrote:
> Attached is a fully-worked-out patch to make SERIAL column default
> expressions refer to the target sequence with a "regclass" literal
> instead of a "text" literal.  Since the regclass literal is actually
> just an OID, it is impervious to renamings and schema changes of
> the target sequence.  This fixes the long-standing hazard of renaming
> a serial column's sequence, as well as the recently added hazard of
> renaming the schema the sequence is in; and it lets us get rid of a
> very klugy solution in ALTER TABLE SET SCHEMA.
> I've arranged for stored regclass literals to create dependencies on
> the referenced relation, which provides useful improvements even for
> handwritten defaults: given
> 	create sequence myseq;
> 	create table foo (f1 int default nextval('myseq'::regclass));
> the system will not allow myseq to be dropped while the default
> expression remains.  (This also ensures that pg_dump will emit the
> sequence before the table.)
> The patch also fixes a couple of places where code was still looking
> at the deprecated pg_attrdef.adsrc column, instead of reverse-compiling
> pg_attrdef.adbin.  This ensures that psql's \d command shows the
> up-to-date form of a column default.  (That should have happened quite
> some time ago; not sure why it was overlooked.)
> I propose applying this to fix the open issue that ALTER SCHEMA RENAME
> breaks serial columns.  Comments, objections?
> 			regards, tom lane

Content-Description: seq-regclass.patch.gz

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  Bruce Momjian                        |
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