From: PG Bug reporting form <noreply@postgresql.org>
To: pgsql-bugs@lists.postgresql.org
Cc: jim@jimkeener.com
Subject: BUG #18097: Immutable expression not allowed in generated at
Date: Fri, 08 Sep 2023 03:47:49 +0000
Message-ID: <18097-ebb179674f22932f@postgresql.org> (raw)
The following bug has been logged on the website:
Bug reference: 18097
Logged by: Jim Keener
Email address: jim@jimkeener.com
PostgreSQL version: 15.0
Operating system: Linux
Description:
Given this table:
CREATE TABLE test_table (
id bigint GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
created_at timestamptz NOT NULL DEFAULT now()
);
The following work:
* alter table test_table add created_local_y text GENERATED ALWAYS AS
(EXTRACT(isoyear FROM created_at AT TIME ZONE 'America/New_York')) STORED;
* alter table test_table add created_local_w text GENERATED ALWAYS AS
(EXTRACT(week FROM created_at AT TIME ZONE 'America/New_York')) STORED;
* alter table test_table add created_local text GENERATED ALWAYS AS
(EXTRACT(isoyear FROM created_at AT TIME ZONE 'America/New_York')::text ||
'|' || EXTRACT(week FROM created_at AT TIME ZONE 'America/New_York')::text)
STORED;
* CREATE INDEX ON test_table ((EXTRACT(isoyear FROM created_at AT TIME ZONE
'America/New_York') || '|' || EXTRACT(week FROM created_at AT TIME ZONE
'America/New_York')));
However, the following DOES NOT work with an error of (ERROR: generation
expression is not immutable):
* alter table test_table add created_local text GENERATED ALWAYS AS
(EXTRACT(isoyear FROM created_at AT TIME ZONE 'America/New_York') || '|' ||
EXTRACT(week FROM created_at AT TIME ZONE 'America/New_York')) STORED;
Given that casting shouldn't "increase" the immutability of an expression,
and expression indexes need also be immutable afaik, I think that there is a
bug somewhere here?
Thank you,
Jim
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Subject: Re: BUG #18097: Immutable expression not allowed in generated at
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