Correct usage of Postgres JSON conversion functions - sql

Question

I am working on a Postgres update transaction.
Let's say I have two tables: events and ticket_books with event booking types. The ticket_books table has a foreign key pointing to the events.
I need to update an event stored in the database, including booking type records from the ticket_books table.
To deal with cascading update and delete, I decided to build a transaction, in a "pseudo-code" it looks like:
BEGIN;
DELETE FROM
ticket_books
WHERE
event_id = ${req.params.id} AND
id NOT IN (${bookingIds})
FOR booking IN json_to_recordset('${JSON.stringify(book)}') as book(id int, title varchar(200), price int, ...) LOOP
IF bookind.id THEN
UPDATE
ticket_books
SET
title = booking.title, price = booking.price
WHERE
event_id = ${req.params.id};
ELSE
INSERT INTO
ticket_books (title, price, qty_available, qty_per_sale)
VALUES
(booking.title, booking.price, booking.qty_available, booking.qty_per_sale)
RETURNING
id
END IF;
END LOOP;
UPDATE
event
SET
...
WHERE
id = ...
RETURNING
id;
COMMIT;
I currently get the error: syntax error at or near "json_to_recordset". I never used json_to_recordset or friends before, just saw from the document that from 9.3 and later those are available. Unsure how to get Postgres to understand what I need, though.
I am embedding a JSON array so the final line looks like:
FOR booking IN json_to_record('[{"id":13,"description":"Three day access to the festival","title":"Three Day General Admission","price":260,"qty_available":5000,"qty_per_sale":10},{"id":14,"description":"Single day access to the festival","title":"Single Day General Admission","price":"90.90","qty_available":2000,"qty_per_sale":2},{"title":"Free Admission","price":"0.00","qty_available":0,"qty_per_sale":0}]')
I believe that my JSON array is valid. Apparently, this is not how I should be passing it to the Postgres. What should I be doing instead? My goal is to iterate over the array entries. If there is an integer value for booking.id, I want to update the record, else insert a new one.

Answer 1

You need a query, and a standalone function call usually does not count as a query:
FOR booking IN select * from json_to_recordset(...
Also, you can't use BEGIN to start a transaction in plpgsql. It is only used to start a block. If you are using a procedure rather than a function, then you can COMMIT but then a new transaction starts immediately with no BEGIN token being used.
You are also missing a semicolon between the DELETE and the FOR, but from the error message that seems to be missing from only your post, and not from your actual code.