Feedback-ID: ia2694551:Fastmail
Date: Fri, 12 Jan 2024 10:58:21 +0100
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: jian he <jian.universality@gmail.com>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: alter table add x wrong error position
Message-ID: <202401120958.2axtexbxpigq@alvherre.pgsql>
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On 2024-Jan-08, jian he wrote:

> hi.
> Maybe this is a small printout err_position bug.
> 
> create table atacc2 ( test int, a int, b int) ;
> success tests:
> alter table atacc2 add CONSTRAINT x PRIMARY KEY (id, b );
> alter table atacc2 add CONSTRAINT x PRIMARY KEY (id, b a);
> alter table atacc2 add CONSTRAINT x PRIMARY KEYa (id, b);
> 
> tests have problem:
> alter table atacc2 add constraints x unique (test, a, b);
> ERROR:  syntax error at or near "("
> LINE 1: alter table atacc2 add constraints x unique (test, a, b);
> 
>           ^
> ADD either following with the optional keyword "COLUMN" or
> "CONSTRAINT"  as the doc.
> so I should expect the '^' point at "constraints"?

Here you're saying to add a column called constraints, of
type x; then UNIQUE is parsed by columnDef as ColQualList, which goes to
the ColConstraintElem production starting with the UNIQUE keyword: 

			| UNIQUE opt_unique_null_treatment opt_definition OptConsTableSpace

so the next thing could be opt_unique_null_treatment or opt_definition
or OptConsTableSpace or going back to ColQualList, but none of those
start with a '(' parens.  So the ( doesn't have a match and you get the
syntax error.

If you don't misspell CONSTRAINT as "constraints", there's no issue.

I don't see any way to improve this.  You can't forbid misspellings of
the keyword CONSTRAINT, because they can be column names.

alter table atacc2 add cnstrnt x unique (test, a, b);
ERROR:  error de sintaxis en o cerca de «(»
LÍNEA 1: alter table atacc2 add cnstrnt x unique (test, a, b);
                                                 ^

-- 
Álvaro Herrera        Breisgau, Deutschland  —  https://www.EnterpriseDB.com/