Postgres 16

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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 integer, root_id integer, parent_id integer, status text, ts timestamp, comment text);
insert into the_table values
(1, null, null, 'COMPLETE', now()-'92d'::interval, '>90 days old, complete, standalone'),
(2, null, null, 'COMPLETE', now()-'92d'::interval, '>90 days old, complete, root of 3,4'),
(3, 2,    null, 'COMPLETE', now()-'92d'::interval, '>90 days old, complete, child of 2, parent of 4'),
(4, 2,    3,    'OPEN',     now()-'92d'::interval, '>90 days old, open, child of 2,3'),
(5, null, null, 'COMPLETE', now()-'92d'::interval, '>90 days old, complete, root of 6,7'),
(6, 5,    null, 'COMPLETE', now()-'92d'::interval, '>90 days old, complete, child of 5, parent of 4'),
(7, 5,    6,    'COMPLETE', now()-'10d'::interval, '<=90 days old, complete, child of 5,6' )
returning *;

CREATE TABLE




id
root_id
parent_id
status
ts
comment


1
null
null
COMPLETE
2023-08-09 11:59:05.826174
>90 days old, complete, standalone

2
null
null
COMPLETE
2023-08-09 11:59:05.826174
>90 days old, complete, root of 3,4

3
2
null
COMPLETE
2023-08-09 11:59:05.826174
>90 days old, complete, child of 2, parent of 4

4
2
3
OPEN
2023-08-09 11:59:05.826174
>90 days old, open, child of 2,3

5
null
null
COMPLETE
2023-08-09 11:59:05.826174
>90 days old, complete, root of 6,7

6
5
null
COMPLETE
2023-08-09 11:59:05.826174
>90 days old, complete, child of 5, parent of 4

7
5
6
COMPLETE
2023-10-30 11:59:05.826174
<=90 days old, complete, child of 5,6



INSERT 0 7


/*
--https://stackoverflow.com/q/77451429/5298879
Delete all the records from the table which are 
 - older than 90 days 
 - in `COMPLETE` status. 

If a row has a `root_id` or a `parent_id` and is `OPEN`, 
then the `root_id` and the `parent_id` rows should not be deleted. 

In the above table, the row with `id=1` should be deleted.

`id=2` and `id=3` are `COMPLETE` and older than 90 days but since `id=4` is `OPEN` and has `root_id=2` and `parent_id=3`, these three rows (`id in (2,3,4)`) should not be deleted. 

`id=5`,`id=6` and `id=7` are all `COMPLETE` but `id=7` is not older than 90 days and has `root_id=5` and `parent_id=6`, so these three rows (`id=5`,`id=6` and `id=7`) should not be deleted.

I tried multiple ways with inner queries 
but I am not able to write a query for this scenario.
*/
--https://stackoverflow.com/a/77452714/5298879
begin work;

DELETE FROM the_table t1
WHERE 'COMPLETE'=status AND now()-ts > '90d'::interval
AND NOT EXISTS (SELECT FROM the_table AS t2
                WHERE (   t1.id IN(t2.root_id,t2.parent_id)
                       OR t2.id IN(t1.root_id,t1.parent_id) )
                  AND (   'OPEN'=t2.status
                       OR now()-t2.ts <= '90d'::interval    )  )
RETURNING *;

rollback;

BEGIN




id
root_id
parent_id
status
ts
comment


1
null
null
COMPLETE
2023-08-09 11:59:05.826174
>90 days old, complete, standalone



DELETE 1



ROLLBACK


insert into the_table values
(8, null, null, 'COMPLETE', now()-'10d'::interval, '<=90 days old, complete, standalone'),
(9, null, null, 'COMPLETE', now()-'10d'::interval, '<=90 days old, complete, root of 10'),
(10,9,    null, 'COMPLETE', now()-'92d'::interval, '>90 days old, complete, child of 9' ),
(11,11,   null, 'COMPLETE', now()-'92d'::interval, '>90 days old, complete, parent/child of self'),
(12,null, 12,   'COMPLETE', now()-'92d'::interval, '>90 days old, complete, parent/child of self'),
(13,14,   null, 'COMPLETE', now()-'92d'::interval, '>90 days old, complete, cross-parent/child of 14'),
(14,13,   null, 'COMPLETE', now()-'92d'::interval, '>90 days old, complete, cross-parent/child of 13'),
(15,null, null, 'COMPLETE', now()-'92d'::interval, '>90 days old, complete, parent of 16,17'),
(16,null, 15,   'COMPLETE', now()-'92d'::interval, '>90 days old, complete, child of 15'),
(17,null, 15,   'OPEN',     now()-'10d'::interval, '<=90 days old, open, child of 15');

table the_table;

INSERT 0 10




id
root_id
parent_id
status
ts
comment


1
null
null
COMPLETE
2023-08-09 11:59:05.826174
>90 days old, complete, standalone

2
null
null
COMPLETE
2023-08-09 11:59:05.826174
>90 days old, complete, root of 3,4

3
2
null
COMPLETE
2023-08-09 11:59:05.826174
>90 days old, complete, child of 2, parent of 4

4
2
3
OPEN
2023-08-09 11:59:05.826174
>90 days old, open, child of 2,3

5
null
null
COMPLETE
2023-08-09 11:59:05.826174
>90 days old, complete, root of 6,7

6
5
null
COMPLETE
2023-08-09 11:59:05.826174
>90 days old, complete, child of 5, parent of 4

7
5
6
COMPLETE
2023-10-30 11:59:05.826174
<=90 days old, complete, child of 5,6

8
null
null
COMPLETE
2023-10-30 11:59:05.846666
<=90 days old, complete, standalone

9
null
null
COMPLETE
2023-10-30 11:59:05.846666
<=90 days old, complete, root of 10

10
9
null
COMPLETE
2023-08-09 11:59:05.846666
>90 days old, complete, child of 9

11
11
null
COMPLETE
2023-08-09 11:59:05.846666
>90 days old, complete, parent/child of self

12
null
12
COMPLETE
2023-08-09 11:59:05.846666
>90 days old, complete, parent/child of self

13
14
null
COMPLETE
2023-08-09 11:59:05.846666
>90 days old, complete, cross-parent/child of 14

14
13
null
COMPLETE
2023-08-09 11:59:05.846666
>90 days old, complete, cross-parent/child of 13

15
null
null
COMPLETE
2023-08-09 11:59:05.846666
>90 days old, complete, parent of 16,17

16
null
15
COMPLETE
2023-08-09 11:59:05.846666
>90 days old, complete, child of 15

17
null
15
OPEN
2023-10-30 11:59:05.846666
<=90 days old, open, child of 15



SELECT 17


begin work;

DELETE FROM the_table t1
WHERE 'COMPLETE'=status
  AND now()-ts > '90d'::interval
  AND NOT EXISTS (SELECT FROM the_table AS t2
                  WHERE (   'OPEN'=t2.status
                         OR now()-t2.ts <= '90d'::interval    )
                    AND (   t1.id IN(t2.root_id,t2.parent_id)
                         OR t2.id IN(t1.root_id,t1.parent_id) )  )
RETURNING *;

rollback;

BEGIN




id
root_id
parent_id
status
ts
comment


1
null
null
COMPLETE
2023-08-09 11:59:05.826174
>90 days old, complete, standalone

11
11
null
COMPLETE
2023-08-09 11:59:05.846666
>90 days old, complete, parent/child of self

12
null
12
COMPLETE
2023-08-09 11:59:05.846666
>90 days old, complete, parent/child of self

13
14
null
COMPLETE
2023-08-09 11:59:05.846666
>90 days old, complete, cross-parent/child of 14

14
13
null
COMPLETE
2023-08-09 11:59:05.846666
>90 days old, complete, cross-parent/child of 13

16
null
15
COMPLETE
2023-08-09 11:59:05.846666
>90 days old, complete, child of 15



DELETE 6



ROLLBACK

id	root_id	parent_id	status	ts	comment
1	null	null	COMPLETE	2023-08-09 11:59:05.826174	>90 days old, complete, standalone
2	null	null	COMPLETE	2023-08-09 11:59:05.826174	>90 days old, complete, root of 3,4
3	2	null	COMPLETE	2023-08-09 11:59:05.826174	>90 days old, complete, child of 2, parent of 4
4	2	3	OPEN	2023-08-09 11:59:05.826174	>90 days old, open, child of 2,3
5	null	null	COMPLETE	2023-08-09 11:59:05.826174	>90 days old, complete, root of 6,7
6	5	null	COMPLETE	2023-08-09 11:59:05.826174	>90 days old, complete, child of 5, parent of 4
7	5	6	COMPLETE	2023-10-30 11:59:05.826174	<=90 days old, complete, child of 5,6