accessing list from json and iterating in postgres - postgresql-9.6

Question

I have a json as mentioned below,
{
"list": [{
"notificationId": 123,
"userId": 444
},
{
"notificationId": 456,
"userId": 789
}
]
}
I need to write a postgres procedure which interates through the list and perform either update/insert based on notification id is already present or not in DB.
I have a notification table which has notificationid and userID as columns.
Can anyone please tell me on how to perform this using postgres json operators.

Answer 1

Try this query:
SELECT *
FROM yourTable
WHERE col->'list'#>'[{"notificationId":123}]';
You may replace the value 123 with whatever notificationId you want to search. Follow the link below for a demo showing that this logic works:
Demo

Answer 2

Assuming you have a unique constraint on notificationid (e.g. because it's the primary key, there is no need for stored function or loop:
with data (j) as (
values ('
{
"list": [{
"notificationId": 123,
"userId": 444
},
{
"notificationId": 456,
"userId": 789
}
]
}'::jsonb)
)
insert into notification (notificationid, userid)
select (e.r ->> 'notificationId')::int, (e.r ->> 'userId')::int
from data d, jsonb_array_elements(d.j -> 'list') as e(r)
on conflict (notificationid) do update
set userid = excluded.userid;
The first step in that statement is to turn the array into a list of rows, this is what:
select e.*
from data d, jsonb_array_elements(d.j -> 'list') as e(r)
does. Given your sample JSON, this returns two rows with a JSON value in each:
r
--------------------------------------
{"userId": 444, "notificationId": 123}
{"userId": 789, "notificationId": 456}
This is then split into two integer columns:
select (e.r ->> 'notificationId')::int, (e.r ->> 'userId')::int
from data d, jsonb_array_elements(d.j -> 'list') as e(r)
So we get:
int4 | int4
-----+-----
123 | 444
456 | 789
And this result is used as the input for an INSERT statement.
The on conflict clause then does an insert or update depending on the presence of the row identified by the column notificationid which has to have a unique index.

Answer 3

Meanwhile i tried this,
CREATE OR REPLACE FUNCTION insert_update_notifications(notification_ids jsonb) RETURNS void AS
$$
DECLARE
allNotificationIds text[];
indJson jsonb;
notIdCount int;
i json;
BEGIN
FOR i IN SELECT * FROM jsonb_array_elements(notification_ids)
LOOP
select into notIdCount count(notification_id) from notification_table where notification_id = i->>'notificationId' ;
IF(notIdCount = 0 ) THEN
insert into notification_table(notification_id,userid) values(i->>'notificationId',i->>'userId');
ELSE
update notification_table set userid = i->>'userId' where notification_id = i->>'notificationId';
END IF;
END LOOP;
END;
$$
language plpgsql;
select * from insert_update_notifications('[{
"notificationId": "123",
"userId": "444"
},
{
"notificationId": "456",
"userId": "789"
}
]');
It works.. Please review this.