Postgres jsonb complex query

Question

I have a table on PostgreSQL 10 that looks like:

CREATE TABLE forms (id serial, form jsonb);
INSERT INTO forms (id, form) VALUES (
 1, '"permissions": [ {"name": "perm-name-1", "who":["group1", "group2",]},
 {"name": "perm-name-2", "who":["group1", "group3"]}]');
INSERT INTO forms (id, form) VALUES (
 2, '"permissions": [ {"name": "perm-name-1", "who":["group5", "group6"]},
 {"name": "perm-name-2", "who":["group7", "group8"]}]');

The JSON for column "form" has more key-value pairs which are irrelevant here.

I need to query based on the permissions "name" and one or more "who" values e.g. :

1. Get all rows whose permission "name" is "perm-name-1" and "who" is any of "group1", "group5" should match all the rows of the example above.
2. Get all rows whose permission "name" is "perm-name-1" and "who" is just "group1" should match row with id 1.

Also, any insight/comment on a JSON schema which would help the database to perform better is welcomed!

Answer 1

I think the first level of arrays is not useful, especially if you are going to retrieve permissions by name.

I would store it like this:

CREATE TABLE forms (id serial, form jsonb);
INSERT INTO forms (id, form) VALUES 
(1, '{"permissions": 
 {"perm-name-1": {"who": ["group1","group2"]}, 
 "perm-name-2": {"who": ["group1","group3"]}}
 }'), 
(2, '{"permissions": 
 {"perm-name-1": {"who": ["group5","group6"]}, 
 "perm-name-2": {"who": ["group7","group8"]}}
 }');

Then both your queries are quite easy to write:

For the first one you can use the "any" operator ?|:

select *
from forms
where form -> 'permissions' -> 'perm-name-1' -> 'who' ?| array['group1', 'group5']

For the second one, the ? operator is enough:

select *
from forms
where form -> 'permissions' -> 'perm-name-1' -> 'who' ? 'group1'

---

You didn't ask for it, but you can also query for rows where a specific permissions contains all specified groups. That can be done using the ?& operator. The following would return the row with ID=1

select *
from forms
where form -> 'permissions' -> 'perm-name-1' -> 'who' ?& array['group1', 'group2'];

The following would return nothing:

select *
from forms
where form -> 'permissions' -> 'perm-name-1' -> 'who' ?& array['group2', 'group3'];

• Vagelis Savvas: Thanx for it! How much more complicated do the queries become with the original schema? Can you provide an example? Should I create a GIN as well?
• user1822: @VagelisS: with the original structure you need to unnest the array (using jsonb_each()) every time you want to find something in the array.