How to query nested JSONB postgres in Rails - ruby-on-rails

Question

I've a table called Order with a jsonb column type called line_items. The line_items column can contain nested values like this:
[
{
"id":9994857545813,
"sku":"CLIPPING-PATH_C2_24H",
},
{
"id":9994857578581,
"sku":"NATURAL-SHADOW_C1_24H",
}
]
The above example has two line items in it but it can vary from 1 to any number of line items.
I need to query all orders that contains only 1 line item where sku = a particular value such as CLIPPING-PATH_C2_24H as per above example.
So, the query should not match the above example but the following that has only 1 line item and sku=CLIPPING-PATH_C2_24H
[
{
"id":9994857545813,
"sku":"CLIPPING-PATH_C2_24H",
}
]
Can any help to write the query using Rails active record?

Answer 1

demo
You can call plpghsql in ruby.(How to call plpgsql functions from Ruby on rails?)
sql query: select jsonb_path_query(order_json,'$[*] ? (#.sku == "CLIPPING-PATH_C2_24H")') from orders ;
it's not easy to get it right, since some part of PL/pgsql function string even include 4 single quotes. Better use raise notice to test it step by step.
CREATE OR REPLACE FUNCTION get_sku_CLIPPING_path (_sku text)
RETURNS json
AS $$
DECLARE
_sql text;
_returnjson jsonb;
BEGIN
RAISE NOTICE '%: _sku', $1;
RAISE NOTICE '%', '$[*] ? (#.sku == ' || $1 || ')';
RAISE NOTICE '%', $s$
SELECT
jsonb_path_query(order_json, $s$ || '''' || '$[*] ? (#.sku == ' || $1 || ')''' || ' from orders';
_sql := $s$
SELECT
jsonb_path_query(order_json, $s$ || '''' || '$[*] ? (#.sku == ' || $1 || ')''' || ' )from orders';
EXECUTE _sql
USING _sku INTO _returnjson;
RETURN (_returnjson::json);
END
$$
LANGUAGE plpgsql;
call it: select * from get_sku_CLIPPING_path('"CLIPPING-PATH_C2_24H"');

Answer 2

First things first, you don't have a nested json. You just have a json array with objects. Moreover your json objects can be representable as tabular. It's better to store those objects in another table and setup a one to many relationship.
You can have an "orders" table and an "order_details" table.
To get data you need, first we need to find records which have "sku":"CLIPPING-PATH_C2_24H" then we need to parse json and get that object from line_items fields.
SELECT
t.*
FROM orders o,
-- extract object from array of json objects
LATERAL jsonb_path_query(o.line_items, '$[*] ? (#.sku == $value)', '{"value" : "CLIPPING-PATH_C2_24H"}') order_line,
-- convert "sku":"NATURAL-SHADOW_C1_24H" into columns
LATERAL jsonb_to_record(order_line) as t(id bigint, sku text)
WHERE
-- find record which has "sku":"NATURAL-SHADOW_C1_24H"
o.line_items #> '[{"sku":"NATURAL-SHADOW_C1_24H"}]';
Result will be like this;
id | sku
------------- | --------------------
9994857545813 | CLIPPING-PATH_C2_24H
fiddle is here

Answer 3

I was able to figure this out using the jsonb_array_length method:
Order
.where("line_items #> ?", [{sku: sku}].to_json)
.where("jsonb_array_length(line_items) = 1")
.count
end
The following resource was extremely helpful:
https://gist.github.com/mankind/1802dbb64fc24be33d434d593afd6221