Recursive query in PostgreSQL to create a Menu tree - postgresql

Question

How to create a json of a hierarchical structure in SQL with PostgreSQL 12?
I need to create a menu like the image below, this menu is already working, but the solution I am using is not very optimized and has a great overhead because I am making many accesses to the database in PHP code with foreach and recursion.
I would like a solution to access the database only once and get the JSON tree ready.
I made a SQL code that is not working very well because it is not merging menu items from the same parent
My current test implementation in SQL is failing, because it is repeating "Jubarte", it is not merging the items of "Jubarte":
CREATE TABLE menus
(
id bigserial NOT NULL PRIMARY KEY,
customer_id integer NOT NULL,
"idPai" bigint,
label text,
rota text
);
INSERT INTO menus(customer_id, "idPai", label, rota) VALUES
(1,NULL,'Jubarte', ''),
(2,1,'Cadastros', ''),
(3,NULL,'Ciente', ''),
(4,1,'Autorizações', ''),
(5,4,'Menus', ''),
(6,2,'Organograma', ''),
(7,1,'Minha Conta', '');
WITH RECURSIVE menus_tree("id", "customer_id", "idPai", "label", "rota", "children") AS (
-- tree leaves (no matching children)
(SELECT c.*, json '[]'
FROM menus c
WHERE NOT EXISTS(SELECT * FROM menus AS hypothetic_child WHERE hypothetic_child."idPai" = c.id)
)
UNION ALL
-- pozs's awesome "little hack"
SELECT (parent).*, json_agg(child) AS "children"
FROM (
SELECT parent, child
FROM menus_tree AS child
JOIN menus parent ON parent.id = child."idPai"
) branch
GROUP BY branch.parent
)
SELECT jsonb_pretty(json_agg(t)::jsonb)
FROM menus_tree t
LEFT JOIN menus AS hypothetic_parent ON(hypothetic_parent.id = t."idPai")
WHERE hypothetic_parent.id IS NULL;
Result:
[
{
"id": 3,
"rota": "",
"idPai": null,
"label": "Ciente",
"children": [
],
"customer_id": 3
},
{
"id": 1,
"rota": "",
"idPai": null,
"label": "Jubarte",
"children": [
{
"id": 7,
"rota": "",
"idPai": 1,
"label": "Minha Conta",
"children": [
],
"customer_id": 7
}
],
"customer_id": 1
},
{
"id": 1,
"rota": "",
"idPai": null,
"label": "Jubarte",
"children": [
{
"id": 2,
"rota": "",
"idPai": 1,
"label": "Cadastros",
"children": [
{
"id": 6,
"rota": "",
"idPai": 2,
"label": "Organograma",
"children": [
],
"customer_id": 6
}
],
"customer_id": 2
},
{
"id": 4,
"rota": "",
"idPai": 1,
"label": "Autorizações",
"children": [
{
"id": 5,
"rota": "",
"idPai": 4,
"label": "Menus",
"children": [
],
"customer_id": 5
}
],
"customer_id": 4
}
],
"customer_id": 1
}
]

Answer 1

I got a solution, I don’t know if it’s the best but it’s working like this, if someone has a better idea, please can suggest
WITH RECURSIVE location_with_level AS (
(
SELECT
menus.*,
0 AS level
FROM
menus,
usuarios u, permissoes P -- <== part to filter by user permissions
WHERE
"idPai" IS NULL
-- part to filter by user permissions
AND u."idPerfil" = P."idPerfil"
AND u."idSistema" = P."idSistema"
AND P."idMenu" = menus."id"
AND u."idPessoa" = 2
AND menus."ativo" = 't'
) UNION ALL
(
SELECT
child.*,
parent.level + 1
FROM
usuarios u, permissoes P, -- <== part to filter by user permissions
menus child
JOIN location_with_level parent ON parent.ID = child."idPai"
-- part to filter by user permissions
WHERE
u."idPerfil" = P."idPerfil"
AND u."idSistema" = P."idSistema"
AND P."idMenu" = child."id"
AND u."idPessoa" = 2
AND child."ativo" = 't'
)
),
-- pega o nivel
maxlvl AS ( SELECT MAX ( level ) maxlvl FROM location_with_level ),
-- generates the JSON of the menu items for each system module
c_tree AS (
(
SELECT location_with_level.*, NULL::JSONB nodes FROM location_with_level, maxlvl WHERE level = maxlvl )
UNION
(
(
SELECT
( branch_parent ).*,
jsonb_agg ( branch_child order by (branch_child->>'ordem')::numeric)
FROM
(
SELECT
branch_parent,
to_jsonb ( branch_child ) /*- 'level' - 'idPai' - 'id'*/ AS branch_child
FROM
location_with_level branch_parent
JOIN c_tree branch_child ON branch_child."idPai" = branch_parent.ID
) branch
GROUP BY
branch.branch_parent
) UNION
(
SELECT C
.*,
NULL :: JSONB
FROM
location_with_level C
WHERE
NOT EXISTS ( SELECT 1 FROM location_with_level hypothetical_child WHERE hypothetical_child."idPai" = C.ID )
)
)
)
SELECT array_to_json(
array_agg(
row_to_json(c_tree)::JSONB /*- 'level' - 'idPai' - 'id'*/ order by sistemas.ordem
)
)::JSONB
AS tree
FROM c_tree
JOIN sistemas on c_tree."idSistema" = sistemas.id
WHERE level=0