Postgres 13

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.

Help with an interesting Postgres question: Why isn't an Index Only Scan used on a partition accessed via the parent table?.

create table test (id int, steps jsonb);

insert into test values
(1, '[]'),
(2, null),
(3, '[{"step_name":"Step1", "status":"success"}]'),
(4, '[{"step_name":"Step1","status":"success","timestamp":1636120240},{"step_name":"Step3","status":"success","timestamp":1636120279}]'),
(5, '[{"step_name":"Step1","status":"fail","timestamp":1636120240},{"step_name":"Step2","status":"success","timestamp":1636120275},{"step_name":"Step3","status":"success","timestamp":1636120279},{"step_name":"Step4","timestamp":1636120236,"status":"success"}]'),
(6, '[{"step_name":"Step3","status":"success","timestamp":1636120240},{"step_name":"Step2","status":"success","timestamp":1636120275},{"step_name":"Step1","status":"success","timestamp":1636120279},{"step_name":"Step4","timestamp":1636120236,"status":"success"}]'),
(7, '[{"step_name":"Step2","status":"success","timestamp":1636120240},{"step_name":"Step1","status":"success","timestamp":1636120275},{"step_name":"Step3","status":"success","timestamp":1636120279},{"step_name":"Step4","timestamp":1636120236,"status":"success"}]'),
(8, '[{"step_name":"Step1","status":"success","timestamp":1636120240},{"step_name":"Step2","status":"success","timestamp":1636120275},{"step_name":"Step3","status":"success","timestamp":1636120279},{"step_name":"Step4","timestamp":1636120236,"status":"success"}]');

CREATE TABLE

INSERT 0 8

id	steps
6	[{"status": "success", "step_name": "Step3", "timestamp": 1636120240}, {"status": "success", "step_name": "Step2", "timestamp": 1636120275}, {"status": "success", "step_name": "Step1", "timestamp": 1636120279}, {"status": "success", "step_name": "Step4", "timestamp": 1636120236}]
7	[{"status": "success", "step_name": "Step2", "timestamp": 1636120240}, {"status": "success", "step_name": "Step1", "timestamp": 1636120275}, {"status": "success", "step_name": "Step3", "timestamp": 1636120279}, {"status": "success", "step_name": "Step4", "timestamp": 1636120236}]
8	[{"status": "success", "step_name": "Step1", "timestamp": 1636120240}, {"status": "success", "step_name": "Step2", "timestamp": 1636120275}, {"status": "success", "step_name": "Step3", "timestamp": 1636120279}, {"status": "success", "step_name": "Step4", "timestamp": 1636120236}]

SELECT 3