Juste pour éviter le double travail, voici les données (j'ai remplacé la baie limite supérieure inclusive par une baie exclusive, ce qui est plus courant, à mon humble avis):
-- CREATE SCHEMA tmp;
DROP TABLE tmp.gaps CASCADE;
CREATE TABLE tmp.gaps
( id INTEGER NOT NULL PRIMARY KEY -- surrogate key
, ztype CHAR(1) NOT NULL
, start_datetime TIMESTAMP NOT NULL -- lower boundary := inclusive
, end_datetime TIMESTAMP NOT NULL -- upper boundary := exclusive
);
CREATE UNIQUE INDEX gaps_forward ON tmp.gaps(ztype,start_datetime);
CREATE UNIQUE INDEX gaps_backward ON tmp.gaps(ztype,end_datetime);
INSERT INTO tmp.gaps(id,ztype,start_datetime,end_datetime) VALUES
(1,'a', '2012-01-11 00:00:00', '2012-01-15 00:00:00' )
,(2,'a', '2012-01-18 00:00:00', '2012-01-21 00:00:00' )
,(3,'b', '2012-01-14 00:00:00', '2012-01-20 00:00:00' )
,(4,'c', '2012-01-10 00:00:00', '2012-01-16 00:00:00' )
,(5,'d', '2012-01-11 00:00:00', '2012-01-21 00:00:00' )
,(6,'e', '2012-01-11 00:00:00', '2012-01-15 00:00:00' ) -- added this
,(7,'e', '2012-01-15 00:00:00', '2012-01-21 00:00:00' ) -- and this
;
-- SELECT * FROM tmp.gaps;
MISE À JOUR :voici le CTE. Dans la première UNION, j'ajoute deux faux intervalles à gauche et à droite de l'intervalle souhaité (12-Jan -- 19-Jan).
Par ztype, je compte le nombre total d'intervalles. Cela devrait être un s'il n'y a pas de trous, deux s'il y a un trou, etc. Cela trouvera également des lacunes pour les ztypes qui n'ont aucun enregistrement dans l'intervalle souhaité.
-- EXPLAIN ANALYZE
WITH RECURSIVE meuk(ztype,start_datetime,end_datetime) AS (
-- For every possible "ztype" add two dummie records
-- just before and just after our wanted interval.
WITH plus2 AS (
SELECT g0.ztype,g0.start_datetime,g0.end_datetime FROM tmp.gaps g0
WHERE (g0.start_datetime <= '2012-01-12 00:00:00' AND g0.end_datetime >= '2012-01-12 00:00:00')
OR (g0.start_datetime >= '2012-01-12 00:00:00' AND g0.end_datetime <= '2012-01-19 00:00:00')
OR (g0.start_datetime <= '2012-01-19 00:00:00' AND g0.end_datetime >= '2012-01-19 00:00:00')
UNION ALL SELECT DISTINCT g1.ztype, '1900-01-01 00:00:00'::timestamp, '2012-01-12 00:00:00'::timestamp FROM tmp.gaps g1
UNION ALL SELECT DISTINCT g2.ztype, '2012-01-19 00:00:00'::timestamp, '2100-01-01 00:00:00'::timestamp FROM tmp.gaps g2
)
SELECT p0.ztype,p0.start_datetime,p0.end_datetime
FROM plus2 p0
-- the start of a stretch: there is no older overlapping
-- (or touching) interval
WHERE NOT EXISTS (SELECT *
FROM plus2 nx
WHERE nx.ztype = p0.ztype
AND nx.start_datetime < p0.start_datetime -- older
AND nx.end_datetime >= p0.start_datetime -- touching or overlapping
)
UNION
SELECT mk.ztype
, LEAST(mk.start_datetime,p1.start_datetime)
, GREATEST(mk.end_datetime,p1.end_datetime)
FROM plus2 p1
, meuk mk
WHERE p1.ztype = mk.ztype
AND (p1.start_datetime >= mk.start_datetime AND p1.start_datetime <= mk.end_datetime AND p1.end_datetime > mk.end_datetime)
)
SELECT ztype, COUNT(*)-1 AS ngap
FROM meuk mk
WHERE NOT EXISTS (SELECT *
FROM meuk nx
WHERE nx.ztype = mk.ztype
AND (nx.start_datetime,nx.end_datetime) OVERLAPS( mk.start_datetime,mk.end_datetime)
AND (nx.end_datetime - nx.start_datetime) > (mk.end_datetime - mk.start_datetime)
)
GROUP BY ztype
ORDER BY ztype
;
La création de la somme finale est laissée en exercice au lecteur;-)
RÉSULTATS :
ztype | ngap
-------+------
a | 1
b | 1
c | 1
d | 0
e | 0
(5 rows)
