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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 A(ars INT, bill INT, codt TEXT, c4 INT);
Insert Into A Values(900,603121,'',123),
(900,603121,'YPR-003',234),
(900,603121,'Psp-123',345),
(900,603121,'',456),
(900,603121,'',567);
Create Table B(ars INT, bill INT, codt TEXT, s4 TEXT);
Insert Into B Values(900,603121,'Psp-123','asd'),
(900,603121,'','zxc'),
(900,455000,'','F');
CREATE TABLE
INSERT 0 5
CREATE TABLE
INSERT 0 3
SELECT a.ars, a.bill, b.codt, a.c4, b.s4
FROM
(
select ars, bill,
case
when
exists(select 1 from B d where d.ars=t.ars and d.bill=t.bill and d.codt= t.codt) then codt
else ''
end as codt, c4
from A t
) a
LEFT JOIN B b ON
a.ars = b.ars AND a.bill = b.bill AND a.codt = b.codt
order by c4
| ars | bill | codt | c4 | s4 |
|---|---|---|---|---|
| 900 | 603121 | 123 | zxc | |
| 900 | 603121 | 234 | zxc | |
| 900 | 603121 | Psp-123 | 345 | asd |
| 900 | 603121 | 456 | zxc | |
| 900 | 603121 | 567 | zxc |
SELECT 5