Postgres 15

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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 mytable (
  id int,
  status varchar(20),
  outgoing json
);
insert into mytable values
(1,	'paid',	'{"a945248027_14454878":"processing"}'),
(2,	'unpaid',	'{"old.a945248027_14454878":"cancelled"}');

CREATE TABLE

INSERT 0 2

select id, status, substring(outgoing::varchar from ':"([a-z]*)' )
from mytable t

id
status
substring

1
paid
processing

2
unpaid
cancelled

SELECT 2