[Bug]: Timezone parameter to time_bucket_gapfill that is not a constant gives error

[mkindahl]

What type of bug is this?

Unexpected error

What subsystems and features are affected?

Query executor

What happened?

Using time_bucket_gapfill with a non-constant timezone parameter gives an error. In this case, using coalesce.

TimescaleDB version affected

2.17.2

PostgreSQL version used

14.14, 17.2

What operating system did you use?

Ubuntu 24.04.1 LTS

What installation method did you use?

Source

What platform did you run on?

On prem/Self-hosted

Relevant log output and stack trace

ERROR:  attribute number 2 exceeds number of columns 1

How can we reproduce the bug?

create table property (
  property_id serial,
  timezone_label text
);

create table metrics (
    property_id int,
    time timestamptz
);

insert into property(timezone_label) values
       ('UTC'),
       (NULL),
       ('Europe/Stockholm'),
       ('WADT');

select count(*) as nprops from property \gset

insert into metrics(time, property_id)
select time, (:nprops * random())::int
from generate_series('2024-12-01T00:00:00Z'::timestamptz,
	             '2025-01-31T00:00:00Z'::timestamptz,
		     '10 minutes') time;

SELECT time_bucket_gapfill('1 day', time, timezone_label) AS day
  FROM metrics JOIN property USING (property_id)
 WHERE time > '2021-12-31 00:00:00+00'::timestamptz
   AND time < '2022-01-10 00:00:00-00'::timestamptz
GROUP BY day
ORDER BY day desc;