Prepared Statement Does Not Exists, PostgreSQL - postgresql

Question

I created the stored procedure with this code
CREATE PROCEDURE get_conferences_for_attendee
(
IN start_time TIMESTAMP,
IN end_time TIMESTAMP,
IN email VARCHAR(255),
IN deleted BOOLEAN
)
AS
$$
SELECT c.localuuid, c.title, i.id, i.start_time, i.end_time, i.status, a.email, a.deleted
FROM Conference c
INNER JOIN Instance i ON i.conference_localuuid = c.localuuid
INNER JOIN Conference_Attendees ca ON ca.conference_localuuid = c.localuuid
INNER JOIN Attendee a ON ca.attendees_localuuid = a.localuuid
WHERE i.start_time BETWEEN start_time AND end_time
AND a.email = email
AND a.deleted = deleted
$$ LANGUAGE SQL;
and this returned
CREATE PROCEDURE
I can see my procedure
SELECT proname, prorettype
FROM pg_proc
WHERE pronamespace = (SELECT oid FROM pg_namespace WHERE nspname = 'public');
proname | prorettype
------------------------------+------------
get_conferences_for_attendee | 2278
When I try to execute, I get the error on the title.
EXECUTE get_conferences_for_attendee ('2022-12-26T00:00:00', '2023-01-01T23:59:59', 'yacs.demo2#abc.com', false);
ERROR: prepared statement "get_conferences_for_attendee" does not exist
Update
I found a solution but I'm not sure if it's the proper way to create this. It looks too complicated for me.
CREATE TYPE conference_record AS (
localuuid VARCHAR(255),
title VARCHAR(255),
id VARCHAR(255),
start_time TIMESTAMP,
end_time TIMESTAMP,
status VARCHAR(255),
email VARCHAR(255),
deleted BOOLEAN
);
CREATE FUNCTION get_conferences_for_attendee
(
IN start_time TIMESTAMP,
IN end_time TIMESTAMP,
IN email VARCHAR(255),
IN deleted BOOLEAN
)
RETURNS SETOF conference_record AS $$
BEGIN
RETURN QUERY
SELECT c.localuuid, c.title, i.id, i.start_time, i.end_time, i.status, a.email, a.deleted
FROM Conference c
INNER JOIN Instance i ON i.conference_localuuid = c.localuuid
INNER JOIN Conference_Attendees ca ON ca.conference_localuuid = c.localuuid
INNER JOIN Attendee a ON ca.attendees_localuuid = a.localuuid
WHERE i.start_time BETWEEN $1 AND $2
AND a.email = $3
AND a.deleted = $4;
END;
$$ LANGUAGE plpgsql;
SELECT * FROM get_conferences_for_attendee ('2022-12-26T00:00:00', '2023-01-01T23:59:59', 'yacs.demo1#abc.com', false);

Answer 1

As pointed out in the comments, to use a procedure, you need to CALL your_procedure();.
The code you presented looks like you're trying to get something from it, so a function is more suitable - procedures can return data through out and inout parameters or side-effects, like dumping them to an outside table.
The function and type definitions you later added in an edit look fine. If you're planning to feed it directly into a table, you don't need to define the custom type and instead specify RETURNS SETOF your_target_table_name or RETURNS TABLE (LIKE your_target_table_name).
You can also make it LANGUAGE sql - since you're not using anything plpgsql-specific, you don't need the additional overhead that comes with it. You'll just have to remove BEGIN RETURN QUERY and END, leaving just the bare-bones query.
You can also use a regular prepared statement for this:
PREPARE get_conferences_for_attendee(
TIMESTAMP,
TIMESTAMP,
VARCHAR(255),
BOOLEAN ) AS
SELECT
c.localuuid,
c.title,
i.id,
i.start_time,
i.end_time,
i.status,
a.email,
a.deleted
FROM Conference c
INNER JOIN Instance i ON i.conference_localuuid = c.localuuid
INNER JOIN Conference_Attendees ca ON ca.conference_localuuid = c.localuuid
INNER JOIN Attendee a ON ca.attendees_localuuid = a.localuuid
WHERE i.start_time BETWEEN $1 AND $2
AND a.email = $3
AND a.deleted = $4;
And use it exactly like you intially planned to, with an EXECUTE:
EXECUTE get_conferences_for_attendee(
'2022-12-26T00:00:00',
'2023-01-01T23:59:59',
'yacs.demo1#abc.com',
false);
Online demo

Answer 2

I found a solution but I'm not sure if it's the proper way to create this.
A function is the correct way to do this.
It looks too complicated for me.
You are indeed over-complicating the implementation. You don't need to create a type, this can be simplified by using returns table() instead.
You also don't need PL/pgSQL for this. A SQL function will be enough
CREATE FUNCTION get_conferences_for_attendee
(
p_start_time TIMESTAMP,
p_end_time TIMESTAMP,
p_email text,
p_deleted BOOLEAN
)
RETURNS table(localuuid text, title, text, id text, start_time timestamp, end_time timestamp, status text, email text, deleted boolean)
AS
$$
SELECT c.localuuid, c.title, i.id, i.start_time, i.end_time, i.status, a.email, a.deleted
FROM Conference c
INNER JOIN Instance i ON i.conference_localuuid = c.localuuid
INNER JOIN Conference_Attendees ca ON ca.conference_localuuid = c.localuuid
INNER JOIN Attendee a ON ca.attendees_localuuid = a.localuuid
WHERE i.start_time BETWEEN p_start_time AND p_end_time
AND a.email = p_email
AND a.deleted = p_deleted
$$
LANGUAGE sql
stable;
I renamed the parameters with a prefix to avoid a name clash with columns of the same name.
Note that using BETWEEN with timestamp values is usually a bad idea. It's better to use a range query using >= for the lower bound and < for the "next day" of the upper bound
e.g. start_time >= 2022-12-26 00:00:00' and end_time < '2023-01-02 00:00:00'
Your condition would not return rows where the end_time is e.g. 2023-01-01 23:59:59.999