Get a ordered JSON tree from Postgres - json

Question

I'm working on a dynamic menu and I need to get a JSON tree with data to build the options in the interface (using CSS, HTML and JS), based on the constraints defined in three tables ( SQL Fiddle still has postgres 9.6, but I'm using postgres 15.0 )
The general idea is to first find the nodes that point to a file (file IS NOT NULL), which are active (status = A) and which are from subsystem 1 (id_subsystem = 1), as long as the user 1 (id_user = 1) is also active (status = A) and has access permission (according to the users_modules table)
With these records, it would be enough to find each parent recursively related and add them to the tree, but keeping the order defined by the group_order field
users
CREATE TABLE users (
id SMALLINT NOT NULL,
name CHARACTER VARYING(20) NOT NULL,
status CHAR(1) NOT NULL
);
id
name
status
1
John Doe
A
2
Jane Doe
A
3
Duh Doe
I
modules
CREATE TABLE modules (
id SMALLINT NOT NULL,
id_subsystem SMALLINT NOT NULL,
id_master SMALLINT,
group_order SMALLINT NOT NULL,
label CHARACTER VARYING(30) NOT NULL,
file CHARACTER VARYING(30),
icon CHARACTER VARYING(20),
status CHAR(1) NOT NULL
);
INSERT INTO
modules
VALUES
(1,1,NULL,1,'Dashboard','dashboard','dashboard','A'),
(2,1,NULL,2,'Registrations',NULL,'cabinet','A'),
(3,1,2,1,'Customers','customers',NULL,'A'),
(4,1,2,2,'Suppliers','suppliers',NULL,'A'),
(5,1,2,3,'Products','products',NULL,'A'),
(6,1,2,4,'Staff',NULL,NULL,'A'),
(7,1,6,1,'Countries','countries',NULL,'A'),
(8,1,6,2,'States','states',NULL,'A'),
(9,1,6,3,'Cities','cities',NULL,'A'),
(10,1,6,4,'Means of contacts',NULL,NULL,'A'),
(11,1,10,1,'Electronic contacts','electronic_contacts',NULL,'A'),
(12,1,10,2,'Phone contacts','phone_contacts',NULL,'A'),
(13,1,10,3,'Deprecated contacts','deprecated_contacts',NULL,'I'),
(14,1,NULL,3,'Settings','settings','sliders','A'),
(15,2,NULL,1,'Dashboard','dashboard','dashboard','A'),
(16,2,NULL,2,'Financial',NULL,'cash','A'),
(17,2,16,1,'Bills to pay','bills_to_pay',NULL,'A'),
(18,2,16,2,'Bills to receive','bills_to_receive',NULL,'A');
id
id_subsystem
id_master
order
label
file
icon
status
1
1
NULL
1
Dashboard
dashboard
dashboard
A
2
1
NULL
2
Registrations
NULL
cabinet
A
3
1
2
1
Customers
customers
NULL
A
4
1
2
2
Suppliers
suppliers
NULL
A
5
1
2
3
Products
products
NULL
A
6
1
2
4
Staff
NULL
NULL
A
7
1
6
1
Countries
countries
NULL
A
8
1
6
2
States
states
NULL
A
9
1
6
3
Cities
cities
NULL
A
10
1
6
4
Means of contacts
NULL
NULL
A
11
1
10
1
Electronic contacts
electronic_contacts
NULL
A
12
1
10
2
Phone contacts
phone_contacts
NULL
A
13
1
10
3
Deprecated contacts
deprecated_contacts
NULL
I
14
1
NULL
3
Settings
settings
sliders
A
15
2
NULL
1
Dashboard
dashboard
dashboard
A
16
2
NULL
2
Financial
NULL
cash
A
17
2
16
1
Bills to pay
bills_to_pay
NULL
A
18
2
16
2
Bills to receive
bills_to_receive
NULL
A
users_modules
CREATE TABLE users_modules (
id_user SMALLINT NOT NULL,
id_module SMALLINT NOT NULL
);
INSERT INTO
users_modules
VALUES
(1,1),
(1,3),
(1,4),
(1,5),
(1,7),
(1,8),
(1,11),
(1,12);
id_user
id_module
1
1
1
3
1
4
1
5
1
7
1
8
1
11
1
12
I created the query below and it seems to be pretty close to solving the problem, but I still can't figure out what it is
WITH RECURSIVE
sub1 (id_master,sub) AS
(
(
/*
THE FIRST PART OF A RECURSIVE CTE IS FOR NON-RECURSIVE DATA
HERE I GET ALL THE RECORDS THAT POINT TO A FILE THAT CAN BE ACCESSED BY THE USER, BUT ONLY IF IT DOESN'T HAVE THE ROOT AS THE PARENT
*/
SELECT
B.id_master,
JSONB_AGG(
JSONB_BUILD_OBJECT(
'icon',B.icon,
'label',B.label,
'module',B.file
)
ORDER BY
B.group_order
) AS sub
FROM
(
SELECT
X.id_module
FROM
users_modules X
INNER JOIN
users Y
ON
X.id_user=Y.id
WHERE
X.id_user=1 AND
Y.status='A'
) A
INNER JOIN
modules B
ON
A.id_module=B.id
WHERE
B.id_master IS NOT NULL AND
B.id_subsystem=1 AND
B.status='A'
GROUP BY
B.id_master
)
UNION ALL
(
/*
THE SECOND PART OF A RECURSIVE CTE IS FOR RECURSIVE DATA
HERE I ASSEMBLE THE TREE CONNECTING ALL FINAL NODES AND BRANCHES POINTED RECURSIVELY
*/
SELECT
A.id_master,
JSONB_BUILD_OBJECT(
'icon',A.icon,
'label',A.label,
'sub',B.sub
) AS sub
FROM
modules A
INNER JOIN
sub1 B
ON
A.id=B.id_master
WHERE
A.status='A'
ORDER BY
A.group_order
)
)
SELECT
JSONB_AGG(sub ORDER BY group_order)
FROM
(
SELECT
sub,
group_order
FROM
(
(
/*
TYING AT THE ROOT ALL KNOTS POINTING TO THE ROOT
*/
SELECT
JSONB_BUILD_OBJECT(
'icon',A.icon,
'label',A.label,
'sub',B.sub
) AS sub,
A.group_order
FROM
modules A
INNER JOIN
sub1 B
ON
A.id=B.id_master
WHERE
A.id_master IS NULL AND
A.id_subsystem=1 AND
A.status='A'
)
UNION ALL
(
/*
ADDING ALL USER ACCESSIBLE FILE NODES THAT HAVE ROOT AS THE PARENT
*/
SELECT
JSONB_BUILD_OBJECT(
'icon',B.icon,
'label',B.label,
'module',B.file
) AS sub,
B.group_order
FROM
(
SELECT
A.id_module
FROM
users_modules A
INNER JOIN
modules B
ON
A.id_module=B.id
WHERE
A.id_user=1 AND
B.id_master IS NULL AND
B.status='A'
GROUP BY
A.id_module
) A
INNER JOIN
modules B
ON
A.id_module=B.id AND
B.status='A'
)
) sub2
) sub3
What I get is this:
[
{
"icon": "dashboard",
"label": "Dashboard",
"module": "dashboard"
},
{
"icon": "cabinet",
"label": "Registrations",
"sub":
[
{
"icon": null,
"label": "Customers",
"module": "customers"
},
{
"icon": null,
"label": "Suppliers",
"module": "suppliers"
},
{
"icon": null,
"label": "Products",
"module": "products"
}
]
},
{
"icon": "cabinet",
"label": "Registrations",
"sub":
{
"icon": null,
"label": "Staff",
"sub":
[
{
"icon": null,
"label": "Countries",
"module": "countries"
},
{
"icon": null,
"label": "States",
"module": "states"
}
]
}
},
{
"icon": "cabinet",
"label": "Registrations",
"sub":
{
"icon": null,
"label": "Staff",
"sub":
{
"icon": null,
"label": "Means of contacts",
"sub":
[
{
"icon": null,
"label": "Electronic contacts",
"module": "electronic_contacts"
},
{
"icon": null,
"label": "Phone contacts",
"module": "phone_contacts"
}
]
}
}
}
]
But what I need is this:
[
{
"icon": "dashboard",
"label": "Dashboard",
"module": "dashboard"
},
{
"icon": "cabinet",
"label": "Registrations",
"sub":
[
{
"icon": null,
"label": "Customers",
"module": "customers"
},
{
"icon": null,
"label": "Suppliers",
"module": "suppliers"
},
{
"icon": null,
"label": "Products",
"module": "products"
},
{
"icon": null,
"label": "Staff",
"sub":
[
{
"icon": null,
"label": "Countries",
"module": "countries"
},
{
"icon": null,
"label": "States",
"module": "states"
},
{
"icon": null,
"label": "Means of contacts",
"sub":
[
{
"icon": null,
"label": "Electronic contacts",
"module": "electronic_contacts"
},
{
"icon": null,
"label": "Phone contacts",
"module": "phone_contacts"
}
]
}
]
}
]
},
{
"icon": "sliders",
"label": "Settings",
"module": "settings"
}
]
Part of the members of the registrations node was not nested inside it and the settings node was lost
Almost there...

Answer 1

The query here below provides the expected result according to your data set :
WITH RECURSIVE list AS (
SELECT m.id_subsystem
, p.id :: integer AS id_master
, array_agg(m.id :: integer ORDER BY m.group_order) AS children_array
, bool_and(NOT EXISTS(SELECT 1 FROM modules where id_master = m.id)) AS leaves_only
, jsonb_build_object('icon', p.icon, 'label', p.label,'sub', jsonb_agg(jsonb_build_object('icon', m.icon, 'label', m.label, 'module', m.file) ORDER BY m.group_order)) AS module_hierarchy
FROM modules m
LEFT JOIN modules p
ON p.id = m.id_master
GROUP BY m.id_subsystem, p.id, p.icon, p.label
), tree AS (
SELECT id_subsystem
, id_master
, module_hierarchy
FROM list
WHERE leaves_only -- starts with the leaf modules
UNION ALL
SELECT t.id_subsystem
, l.id_master
, jsonb_set(l.module_hierarchy, array['sub', (array_position(l.children_array, t.id_master) - 1) :: text], t.module_hierarchy, true)
FROM tree t
INNER JOIN list l
ON l.children_array #> array[t.id_master] -- bottom-up tree build
AND l.id_subsystem = t.id_subsystem
WHERE t.id_master IS NOT NULL
)
SELECT id_subsystem, jsonb_pretty(module_hierarchy->'sub')
FROM tree
WHERE id_master IS NULL
Some conditions are not implemented yet : status of the modules and users, users_modules relationship, but adding these conditions should not be a big deal.
This query provides the expected result only if there is only one branch with 2 levels or more which is the case in your data set. When there are 2 or more branches with 2 levels or more, we need to merge the branches all together with a dedicated aggregate function :
CREATE OR REPLACE FUNCTION jsonb_merge (x jsonb, y jsonb)
RETURNS jsonb LANGUAGE sql IMMUTABLE AS $$
SELECT jsonb_agg(
CASE
WHEN x.content->>'sub' IS NOT NULL AND y.content->>'sub' IS NOT NULL
THEN (x.content - 'sub') || jsonb_build_object('sub', jsonb_merge(x.content->'sub', y.content->'sub'))
WHEN x.content->>'sub' IS NOT NULL
THEN x.content
ELSE y.content
END
ORDER BY x.id
)
FROM jsonb_path_query(COALESCE(x, y), '$[*]') WITH ORDINALITY AS x(content, id)
INNER JOIN jsonb_path_query(y, '$[*]') WITH ORDINALITY AS y(content, id)
ON x.id = y.id
$$ ;
CREATE OR REPLACE AGGREGATE jsonb_merge(jsonb)
( stype = jsonb, sfunc = jsonb_merge) ;
This aggregate function cannot be called directly inside the recursive query because postgres doesn't accept aggregate functions in the recursive part of the query, but it can be called after :
WITH RECURSIVE list AS (
SELECT m.id_subsystem
, p.id :: integer AS id_master
, array_agg(m.id :: integer ORDER BY m.group_order) AS children_array
, bool_and(NOT EXISTS(SELECT 1 FROM modules where id_master = m.id)) AS leaves_only
, jsonb_build_object('icon', p.icon, 'label', p.label,'sub', jsonb_agg(jsonb_build_object('icon', m.icon, 'label', m.label, 'module', m.file) ORDER BY m.group_order)) AS module_hierarchy
FROM modules m
LEFT JOIN modules p
ON p.id = m.id_master
GROUP BY m.id_subsystem, p.id, p.icon, p.label
), tree AS (
SELECT id_subsystem
, id_master
, module_hierarchy
FROM list
WHERE leaves_only
UNION ALL
SELECT t.id_subsystem
, l.id_master
, jsonb_set(l.module_hierarchy, array['sub', (array_position(l.children_array, t.id_master) - 1) :: text], t.module_hierarchy, true)
FROM tree t
INNER JOIN list l
ON l.children_array #> array[t.id_master]
AND l.id_subsystem = t.id_subsystem
WHERE t.id_master IS NOT NULL
)
SELECT id_subsystem
, jsonb_pretty(jsonb_merge(module_hierarchy->'sub'))
FROM tree
WHERE id_master IS NULL
GROUP BY id_subsystem
This query should work for any kind of trees with any levels.
see test result in dbfiddle