From: Tom Lane <tgl@sss.pgh.pa.us>
To: jian he <jian.universality@gmail.com>
cc: Kirill Reshke <reshkekirill@gmail.com>, Amul Sul <sulamul@gmail.com>,
        PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: Error position support for ComputeIndexAttrs
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Comments: In-reply-to jian he <jian.universality@gmail.com>
	message dated "Sun, 04 Jan 2026 12:19:25 +0800"
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Date: Sun, 04 Jan 2026 12:28:25 -0500
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jian he <jian.universality@gmail.com> writes:
> This will not work for ``ALTER TABLE t ADD CONSTRAINT c UNIQUE (ii);``.
> In this case, gram.y produces a single Constraint node, and Constraint n=
ode
> contain only one location field. However, a unique location is required =
for each
> IndexElem node.

Yeah, the actual problem is that the column name(s) in Constraint are
just a list of String nodes without per-name locations.
transformIndexConstraint throws some errors using constraint->location
that really ought to point at an individual column name, so there's
room for improvement there, as seen in this example from the
regression tests:

-- UNIQUE with a range column/PERIOD that isn't there:
CREATE TABLE temporal_rng3 (
  id INTEGER,
  CONSTRAINT temporal_rng3_uq UNIQUE (id, valid_at WITHOUT OVERLAPS)
);
ERROR:  column "valid_at" named in key does not exist
LINE 3:   CONSTRAINT temporal_rng3_uq UNIQUE (id, valid_at WITHOUT O...
          ^

But this seems like material for a separate patch.

			regards, tom lane