Postgres 13

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

create table the_table 
(
  id int,
  datas json
);

CREATE TABLE


insert into the_table(id, datas)
values
(2, '[{"Value": "", "localId": 14},{"Value": "ccc", "localId":7}]'),
(3, '[{"Value": "", "localId": 14}]'),
(3, '[{"Value": "", "localId": 7}]');

INSERT 0 3


select *
from the_table
where datas::jsonb @> '[{"localId": 7}]';


id
datas


2
[{"Value": "", "localId": 14},{"Value": "ccc", "localId":7}]

3
[{"Value": "", "localId": 7}]



SELECT 2

id	datas
2	[{"Value": "", "localId": 14},{"Value": "ccc", "localId":7}]
3	[{"Value": "", "localId": 7}]