DB

CreateRecordQueue.sql

CREATE OR REPLACE FUNCTION create_record_queue(customer_full_name_in character varying)
RETURNS TABLE(
	customer_full_name character varying,
	queue_number integer,
	operator_place character varying
)
LANGUAGE 'plpgsql'
AS $body$
DECLARE 
	next_operator_id integer;
BEGIN
	LOCK TABLE operators IN ROW EXCLUSIVE MODE;
	
	PERFORM *
	FROM operators as O
	WHERE O.is_working = true;
	IF NOT FOUND THEN
		RAISE 'Not found';
	END IF;

	LOCK TABLE queue IN EXCLUSIVE MODE;
	
	SELECT 
		O.operator_id,
		COALESCE(MAX(Q.queue_number), 0) cnt_clients_in_queue,
		O.operator_place
	INTO next_operator_id, queue_number, operator_place
	FROM operators as O
	LEFT JOIN queue as Q
	ON O.operator_id = Q.operator_id
	WHERE O.is_working = TRUE
	AND (DATE(Q.registration_date) = CURRENT_DATE OR Q.registration_date IS NULL)
	GROUP BY O.operator_id
	ORDER BY cnt_clients_in_queue
	LIMIT 1;

	customer_full_name := customer_full_name_in;
	queue_number := queue_number + 1;

	INSERT INTO queue(operator_id, customer_full_name, queue_number) 
	VALUES (next_operator_id, customer_full_name, queue_number);
 
	RETURN NEXT;
END;
$body$;

EndOperatorService.sql

CREATE OR REPLACE PROCEDURE end_operator_service(operator_id_in integer)
LANGUAGE 'plpgsql'
AS $body$
DECLARE
	var_queue_id integer;
BEGIN
	SELECT Q.queue_id
	INTO var_queue_id
	FROM queue AS Q
	WHERE Q.operator_id = operator_id_in
	AND Q.start_service_date IS NOT NULL
	AND Q.end_service_date IS NULL;

	IF NOT FOUND THEN
		RAISE 'NOT FOUND';
	END IF;
	
	UPDATE queue q
	SET end_service_date = CURRENT_TIMESTAMP
	WHERE queue_id = var_queue_id;
END;
$body$;

EndOperatorWorking.sql

CREATE OR REPLACE PROCEDURE end_operator_working(operator_id_in integer)
LANGUAGE 'plpgsql'
AS $body$
DECLARE
    var_customer_full_name character varying;
    var_queue_number integer;
BEGIN
    PERFORM operator_id
    FROM operators
    WHERE operator_id = operator_id_in
    AND is_working = true;
    IF NOT FOUND THEN
        RETURN;
    END IF;

    SELECT customer_full_name, queue_number
    INTO var_customer_full_name, var_queue_number
    FROM queue
    WHERE start_service_date IS NOT NULL
    AND end_service_date IS NULL
    AND operator_id = operator_id_in;
    IF FOUND THEN
        RAISE 'CustomerFullName = %, QueueNumber = %, still processing',
		var_customer_full_name,
		var_queue_number; 
    END IF;
	
	LOCK TABLE operators IN SHARE MODE;
	
    UPDATE operators
    SET is_working = false
    WHERE operator_id = operator_id_in;
END;
$body$;

StartOperatorService.sql

CREATE OR REPLACE FUNCTION start_operator_service(operator_id_in integer)
RETURNS TABLE( 
	r_customer_full_name character varying,
	r_queue_number integer,
	r_operator_place character varying
)
LANGUAGE 'plpgsql'
AS $body$
DECLARE 
	var_customer_full_name character varying;
	var_queue_number integer;
	var_queue_id integer;
BEGIN
	UPDATE operators
	SET is_working = true
	WHERE operator_id = operator_id_in;

	SELECT Q.customer_full_name, Q.queue_number
	INTO var_customer_full_name, var_queue_number
	FROM queue Q
	WHERE Q.start_service_date IS NOT NULL 
	AND Q.end_service_date IS NULL
	AND Q.operator_id = operator_id_in;
	IF FOUND THEN
		RAISE 'CustomerFullName = %, QueueNumber = %, still processing',
		var_customer_full_name,
		var_queue_number;
	END IF;

	SELECT queue_id, customer_full_name, queue_number
	INTO var_queue_id, r_customer_full_name, r_queue_number
	FROM queue
	WHERE DATE(registration_date) = CURRENT_DATE
	AND start_service_date IS NULL
	AND operator_id = operator_id_in
	ORDER BY queue_number
	LIMIT 1;
	IF NOT FOUND THEN
		RETURN;
	END IF;

	UPDATE queue
	SET start_service_date = CURRENT_TIMESTAMP
	WHERE queue_id = var_queue_id;

	SELECT operator_place
	INTO r_operator_place
	FROM operators
	WHERE operator_id = operator_id_in;

	RETURN NEXT;
END;
$body$;