Using subquery results as a condition of jsonb field indexed search - postgresql

I have two following tables:
CREATE TABLE elements(
id INT PRIMARY KEY,
element_type INT,
api_name VARCHAR(100) UNIQUE
);
CREATE TABLE entries(
id INT PRIMARY KEY,
elements JSONB
)
entries.elements field stored a jsonb-array of elements in following format:
[
{
"id": elements.id
"type": elements.element_type
"value": <some_value>
},
{
"id": elements.id
"type": elements.element_type
"value": <some_value>
}
...
]
The value field can be one of 3 types:
Literal (i.e. "abc", 12, true)
Array of literals (i.e. ["abc", "cbd"], [12, 21])
Array of objects (i.e. [{"node_id": <uuid>, "value": "abc"}, {"node_id": <uuid>, "value": "cba"}])
And I have index (maybe incorrect)
CREATE INDEX some_idx_name
ON entries
USING GIN (elements jsonb_ops)
For example suppose that I have data in these tables:
INSERT INTO elements(id, element_type, api_name) VALUES
(1, 1, 'el_number_1'),
(2, 2, 'el_datetime'),
(3, 3, 'el_files'),
(4, 1, 'el_number_2');
INSERT INTO entries(id, elements) VALUES
(1, '[{"id": 1, "type": 1, "value": 12}, {"id": 3, "type": 3, "value": [1, 2]}]'::JSONB),
(2, '[{"id": 4, "type": 1, "value": 12}, {"id": 2, "type": 2, "value": [{"date": "20.12.2022", "time": "16:18"}]}]'::JSONB);
So if I want to find entry by elements I need to do something like this:
SELECT id
FROM entries
WHERE elements #? '$[*] ? (#.id == 4 && #.value = 12)'
But how can I find entry by value of elements which was found by api_name?
-- DOES NOT WORK (only for example what I need)
SELECT id
FROM entries
WHERE elements #? '$[*] ? (#.id == (SELECT id FROM elements WHERE api_name = 'el_number_2') && #.value = 12)'
Fiddle link

Related

How do I create a Postgres table with a column that holds an array of objects?

The documentation shows that arrays can be created as either text or integer. I did not find an example for creating an object array. An example is the items column:
CREATE TABLE cart (
_id serial PRIMARY KEY,
user_id Integer UNIQUE NOT NULL,
items varchar [],
FOREIGN KEY (user_id)
REFERENCES users (_id)
Object stored in the items array have quotes around them making them strings instead of objects. A code segment creating objects in items is shown below:
update cart
set items =
array_append(items,
'{product_id: ${cartItem.productId}, size: ${cartItem.size}, quantity: ${cartItem.quantity}}')
where _id = ${cart._id}
and user_id = ${userId}
RETURNING *
I am compelled to put quotes around the object value. As a result it is stored as a string in the column with quotes around it.
cart {
_id: 1,
user_id: 1,
items: [
'{product_id: 1, size: Small, quantity: 1}',
'{product_id: 1, size: Small, quantity: 1}',
'{product_id: 1, size: Small, quantity: 1}'
]
}
Because the items in the items column are stored as string instead of objects, I cannot correctly iterate over them in my program. For example,
items.product_id does not exist.
How do I fix this?
I wrote some examples for you
Example 1. (Insert into JSONB type using converting String to JSONB)
INSERT INTO cart
(
product_id,
quantity,
"size",
user_id,
items
)
values
(
1,
1,
'Small',
1,
'[
{"size": "Small", "quantity": 1, "product_id": 1},
{"size": "Small", "quantity": 1, "product_id": 1},
{"size": "Small", "quantity": 1, "product_id": 1}
]'::jsonb
);
Example 2. (Convert fields of selected table to JSONB using row_to_json)
select row_to_json(t1) as your_json from (
select product_id, "size", quantity from cart
) t1
Result:
your_json
--------------------------------------------
{"product_id":1,"size":"Small","quantity":1}
{"product_id":1,"size":"Small","quantity":1}
{"product_id":1,"size":"Small","quantity":1}
Example 3. (Concat all rows of type JSONB)
select jsonb_agg(row_to_json(t1)) as your_json from (
select product_id, "size", quantity from cart
) t1
Result:
your_json
---------------------------------------------------------------------------------------------------------------------------------------------------------
[{"size": "Small", "quantity": 1, "product_id": 1}, {"size": "Small", "quantity": 1, "product_id": 1}, {"size": "Small", "quantity": 1, "product_id": 1}]
Example 4. (Similar of row_to_json)
select
json_build_object('product_id', product_id, 'size', size, 'quantity', quantity) as your_json
from cart;
Result:
your_json
--------------------------------------------
{"product_id":1,"size":"Small","quantity":1}
{"product_id":1,"size":"Small","quantity":1}
{"product_id":1,"size":"Small","quantity":1}
Example 5. (Concatenate many JSONB objects using ||)
select jsonb_build_array('{"product_id":1,"size":"Small","quantity":1}'::jsonb) || jsonb_build_array('{"product_id":1,"size":"Small","quantity":1}'::jsonb) as your_json
-- or
select jsonb_build_array('{"product_id":1,"size":"Small","quantity":1}'::jsonb, '{"product_id":1,"size":"Small","quantity":1}'::jsonb) as your_json
Result:
your_json
------------------------------------------------------------------------------------------------------
[{"product_id": 1, "size": "Small", "quantity": 1}, {"product_id": 1, "size": "Small", "quantity": 1}]
Example 6. (Similar example to your update query (using concatenating JSONB types)
update cart
set
items = jsonb_build_array(items) || jsonb_build_array('{"product_id":1,"size":"Small","quantity":1}'::jsonb)
where id = 1
Result:
items
------------------------------------------------------------------------------------------------------
[{"product_id": 1, "size": "Small", "quantity": 1}, {"product_id": 1, "size": "Small", "quantity": 1}]
Recommended using JSON or JSONB types. In JSON types you can perform any operations on keys or values, such as filtering, selecting, joining. If you need you can even show JSON keys and values as table record view.
Examples:
items: '[
{"product_id": 1, "size": "Small", "quantity": 1},
{"product_id": 1, "size": "Small", "quantity": 1},
{"product_id": 1, "size": "Small", "quantity": 1}
]'
select
json_array_elements(items)->'product_id' as product_id,
json_array_elements(items)->'size' as "size",
json_array_elements(items)->'quantity' as quantity
from cart
where user_id = 1;
Result:
product_id
size
quantity
1
"Small"
1
1
"Small"
1
1
"Small"
1

Postgres JSONB Editing columns

I was going through the Postgres Jsonb documentation but was unable to find a solution for a small issue I'm having.
I've got a table : MY_TABLE
that has the following columns:
User, Name, Data and Purchased
One thing to note is that "Data" is a jsonb and has multiple fields. One of the fields inside of "Data" is "Attribute" but the values it can hold are not in sync. What I mean is, it could be a string, a list of strings, an empty list, or just an empty string. However, I want to change this.
The only values that I want to allow are a list of strings and an empty list. I want to convert all the empty strings to empty lists and regular strings to a list of strings.
I have tried using json_build_array but have not had any luck
So for example, I'd want my final jsonb to look like :
[{
"Id": 1,
"Attributes": ["Test"]
},
{
"Id": 2,
"Attributes": []
},
{
"Id": 3,
"Attributes": []
}]
when converted from
{
"Id": 1,
"Attributes": "Test"
},
{
"Id": 2,
"Attributes": ""
},
{
"Id": 3,
"Attributes": []
}
]
I only care about the "Attributes" field inside of the Json, not any other fields.
I also want to ensure for some Attributes that have an empty string "Attributes": "", they get mapped to an empty list and not a list with an empty string ([] not [""])
I also want to preserve the empty array values ([]) for the Attributes that already hold an empty array value.
This is what I have so far:
jsonb_set(
mycol,
'{Attributes}',
case when js ->> 'Attributes' <> ''
then jsonb_build_array(js ->> 'Attributes')
else '[]'::jsonb
end
)
However, Attributes: [] is getting mapped to ["[]"]
Use jsonb_array_elements() to iterate over the elements of each 'data' cell and jsonb_agg to regroup the transform values together into an array:
WITH test_data(js) AS (
VALUES ($$ [
{
"Id": 1,
"Attributes": "Test"
},
{
"Id": 2,
"Attributes": ""
},
{
"Id": 3,
"Attributes": []
}
]
$$::JSONB)
)
SELECT transformed_elem
FROM test_data
JOIN LATERAL (
SELECT jsonb_agg(jsonb_set(
elem,
'{Attributes}',
CASE
WHEN elem -> 'Attributes' IN ('""', '[]') THEN '[]'::JSONB
WHEN jsonb_typeof(elem -> 'Attributes') = 'string' THEN jsonb_build_array(elem -> 'Attributes')
ELSE elem -> 'Attributes'
END
)) AS transformed_elem
FROM jsonb_array_elements(test_data.js) AS f(elem) -- iterate over every element in the array
) s
ON TRUE
returns
[{"Id": 1, "Attributes": ["Test"]}, {"Id": 2, "Attributes": []}, {"Id": 3, "Attributes": []}]

Postgresql query array of objects in JSONB field filter Specific Object

CREATE TABLE company (id SERIAL, companyJson JSONB);
CREATE INDEX comapny_gin_idx ON company USING gin (companyJson);
INSERT INTO company (id, companyJson)
VALUES (1, '[{"name": "t", "company": "company1"}]');
INSERT INTO company (id, companyJson)
VALUES (2, '[{"name": "b", "company":"company2"}, {"name": "b", "company":"company3"}]');
SELECT * FROM company WHERE companyJson #> '[{"company": "company2" , "name": "b"}]';
The output of the above program is
2 [{"name": "b", "company": "company2"}, {"name": "b", "company": "company3"}]
Is there anyway to return {"name": "b", "company": "company2"} instead whole row.
I can only think of unnesting the array and the return the element from that:
SELECT x.j
FROM company c
cross join jsonb_array_elements(c.companyjson) as x(j)
where x.j = '{"company": "company2" , "name": "b"}'
You can directly return the first component through companyJson -> 0 which contains -> operand returning the first component by argument zero :
SELECT companyJson -> 0 as companyJson
FROM company
WHERE companyJson #> '[{"company": "company2" , "name": "b"}]';
Demo

Reconstruct JSONB Nested Arrays

I have the following JSONB column called value.
create temp table settings as
select
'{"favorites": [
{
"listings": [
{"id": "aa92f346-7a93-4443-949b-4eab0badd983", "version": 1},
{"id": "cd92e346-6b04-3456-050a-5eeb0bddd027", "version": 3},
{"id": "cd92e346-6b04-3456-050a-5eeb0bddd333", "version": 2}
]
}
]}'::jsonb as value;
So I'm trying to remove items from this nested array and reconstruct it like so
select jsonb_set(value,'{favorites}',jsonb_set('{}','{listings}',
jsonb_agg(new_elems)) ) as ne from settings s ,
lateral ( select jsonb_array_elements(elem->'listings')as new_elems
from jsonb_array_elements(value->'favorites')elem) sets where
sets.new_elems->>'id' != 'aa92f346-7a93-4443-949b-4eab0badd983'
group by s.value
Which works but the "favorites" array is flattened.
Instead of
"{"favorites": [{"listings": [{"id": "cd92e346-6b04-3456-050a-5eeb0bddd027", "version": 3}, {"id": "cd92e346-6b04-3456-050a-5eeb0bddd333", "version": 2}]}]}"
I get
"{"favorites": {"listings": [{"id": "cd92e346-6b04-3456-050a-5eeb0bddd027", "version": 3}, {"id": "cd92e346-6b04-3456-050a-5eeb0bddd333", "version": 2}]}}"
Does anyone have an idea on how can I solve this?.
you can create jsonb arrays by using the functions JSONB_AGG or JSON_BUILD_ARRAY. JSONB_AGG is an aggregate function, whereas JSONB_BUILD_ARRAY puts all provided arguments in an array.
Below, I used JSONB_BUILD_ARRAY to make favorites into an json array rather than a key-value
SELECT
JSONB_SET(
'{}', '{favorites}',
JSONB_BUILD_ARRAY(
JSONB_SET('{}', '{listings}', JSONB_AGG(listings))
)
)
FROM settings,
LATERAL (SELECT
JSONB_ARRAY_ELEMENTS(JSONB_ARRAY_ELEMENTS(value->'favorites')->'listings') listings
FROM settings) listings
WHERE listings.listings->>'id' != 'aa92f346-7a93-4443-949b-4eab0badd983'

How can I do less than, greater than in JSON array object Postgres fields?

I want to retrieve data by specific field operation it store array of object. i want to add new object in it.
CREATE TABLE justjson ( id INTEGER, doc JSONB);
INSERT INTO justjson VALUES ( 1, '[
{
"name": "abc",
"age": "22"
},
{
"name": "def",
"age": "23"
}
]');
retrieve data where age is greater then and equal to 23 how is possible
eg using jsonb_array_elements:
t=# with a as (select *,jsonb_array_elements(doc) k from justjson)
select k from a where (k->>'age')::int >= 23;
k
------------------------------
{"age": "23", "name": "def"}
(1 row)