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Subject: BUG #19454: PL/pgSQL mishandling jsonb attribute reference
To: pgsql-bugs@lists.postgresql.org
From: PG Bug reporting form <noreply@postgresql.org>
Cc: ma.sao@msa.hinet.net
Reply-To: ma.sao@msa.hinet.net, pgsql-bugs@lists.postgresql.org
Date: Sun, 12 Apr 2026 15:45:39 +0000
Message-ID: <19454-98a60db746b6dd22@postgresql.org>
Auto-Submitted: auto-generated
Archived-At: <https://www.postgresql.org/message-id/19454-98a60db746b6dd22%40postgresql.org>
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The following bug has been logged on the website:

Bug reference:      19454
Logged by:          CN Liou
Email address:      ma.sao@msa.hinet.net
PostgreSQL version: 18.3
Operating system:   Linux Debian Bookworm
Description:       =20

It appears the PL/pgSQL assignment operator :=3D fails to maintain the
stability of a jsonb attribute reference (from a function result) during a
self-concatenation operation, whereas a SELECT wrapper forces correct
materialization.

DO $$
DECLARE
        v_payload JSONB :=3D '[]'::jsonb;
        tj JSONB;
BEGIN
        tj :=3D '{"delta": [["1221", "1221", "TWD", 577.82, {"tags":
[]}]]}'::jsonb;
        RAISE NOTICE 'Before: %, Delta is Null: %', (v_payload IS NULL),
(tj->'delta' IS NULL);
        v_payload :=3D v_payload || tj->'delta'; -- The problematic line
        --v_payload :=3D (SELECT v_payload || (tj->'delta')); --This avoids
the issue.
        RAISE NOTICE 'After: %', (v_payload IS NULL);
END $$;