Re: BUG #18310: Some SQL commands fail to process duplicate objects with error: tuple already updated by self

Michael Paquier <michael(at)paquier(dot)xyz> 于2024年1月26日周五 10:51写道：

> On Thu, Jan 25, 2024 at 04:00:01AM +0000, PG Bug reporting form wrote:
> > The following query:
> > CREATE ROLE u;
> > DROP ROLE u, u;
> > fails with
> > ERROR: tuple already updated by self
>
> Pas glop.
>
> > Whilst all the other DROP commands, accepting a list of objects (namely,
> > AGGREGATE, DOMAIN, EXTENSION, FOREIGN DATA WRAPPER, FOREIGN TABLE,
> > FUNCTION, INDEX, MATERIALIZED VIEW, OPERATOR, PROCEDURE, ROUTINE,
> > SEQUENCE, SERVER, STATISTICS, TABLE, TYPE, VIEW), handle such duplicates
> > with no error.
>
> DROP ROLE has it own parsing node and its own dropping logic because
> of ACL checks and such, while the others used the unified route with
> dependency.c & friends.
>
> For this job, I think user.c is just overengineered and could be
> simplified to use a list of OIDs. There is no need for ObjectAddress
> or even ObjectAddresses: all of them are created with
> AuthIdRelationId as class ID, and the second loop just fetches the
> role IDs retrieved from the ObjectAddresses created in the first loop.
> We don't use the individual ObjectAddress either. On top of all that,
> it makes the code a bit easier to follow.
>
> > Also, the following ALTER query:
> > CREATE TEXT SEARCH CONFIGURATION ispell_tst (COPY=english);
> > CREATE TEXT SEARCH DICTIONARY ispell (Template=ispell,
> > DictFile=ispell_sample, AffFile=ispell_sample);
> > ALTER TEXT SEARCH CONFIGURATION ispell_tst ALTER MAPPING FOR word, word
> > WITH ispell;
> > fails with the same
> > ERROR: tuple already updated by self
> >
> > Again, I re-checked all the other ALTER commands, that accept a list of
> > objects, and could not find other ones producing the same error.
>
> This one comes down to the list of manipulation of the list for token
> names, where tsearchcmds.c has a few assumptions about the way to do
> its job across multiple catalog scans. We could adjust the code so as
> the list of String nodes is rebuilt with some list_append_unique(),
> but I cannot convince myself that this is worth the complication.
>

I have an idea.
How about using list *res replace int *res in getTokenTypes(), so we can
use list_append_unique().
In outer function, use list *tokens to replace int *tokens, and ntokens =
list_length(tokens) not list_length(stmt->tokentype).

--
> Michael
>

--
Tender Wang
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