holes.sql

/* vim: syntax=pgsql
*/

DROP TABLE IF EXISTS x;
CREATE TABLE IF NOT EXISTS x (
	n integer NOT NULL,
	"offset" integer NOT NULL,
	"size" integer NOT NULL
);

COPY x (n, "offset", "size") FROM stdin;
1	0	10
1	10	10
1	20	10
1	25	15
1	40	10
2	0	10
2	10	10
2	20	10
2	0	40
2	40	10
3	0	10
3	10	10
3	20	10
3	40	10
\.

CREATE OR REPLACE FUNCTION is_full(_n integer, _fullsize integer)
	RETURNS boolean AS $$
DECLARE
	_row record;
	e_offset integer DEFAULT 0;
	e_size integer DEFAULT 0;
BEGIN
	FOR _row IN SELECT "offset", "size" FROM x WHERE x.n = _n ORDER BY "offset"
	LOOP
		-- выходим сразу, если обнаружили пропуск
		IF _row."offset" > e_offset THEN
			return false;
		END IF;
		-- наложение
		IF _row."offset" < e_offset THEN
			-- если не избыточное наложение
			IF _row."offset" + _row."size" > e_offset THEN
				e_offset := _row."offset" + _row."size";
			END IF;
		ELSE
			e_offset := e_offset + _row.size;
		END IF;
		--RAISE NOTICE '%, % -> %', _n ,_row, e_offset;
	END LOOP;

	return (e_offset = _fullsize);
END
$$ LANGUAGE plpgsql;

SELECT n, is_full(n, f), expect
FROM (VALUES(1, 50, True), (2, 50, True), (3, 50, False)) AS r(n, f, expect);