Функция возвращающая запрос, содержащий последовательность дат

WITH ddd AS (
SELECT 
pbegin,
pend,
pFilter,
pPeriod,
CASE WHEN pFilter=FALSE AND pPeriod='hour'      THEN EXTRACT(HOUR   FROM pend-(pbegin + INTERVAL '1 microseconds'))::int4   
     WHEN pFilter=FALSE AND pPeriod='day'       THEN EXTRACT(DAY    FROM pend-(pbegin + INTERVAL '1 microseconds'))::int4 
     WHEN pFilter=FALSE AND pPeriod='week'      THEN EXTRACT(week   FROM pend-(pbegin + INTERVAL '1 microseconds'))::int4
     WHEN pFilter=FALSE AND pPeriod='year'      THEN EXTRACT(YEAR   FROM pend-(pbegin + INTERVAL '1 microseconds'))::int4 
     WHEN pFilter=FALSE AND pPeriod='month'     THEN EXTRACT(MONTH  FROM pend-(pbegin + INTERVAL '1 microseconds'))::int4
     WHEN pFilter=FALSE AND pPeriod='quarter'   THEN EXTRACT(quarter FROM pend-(pbegin + INTERVAL '1 microseconds'))::int4
     WHEN pFilter=FALSE AND pPeriod='year'      THEN EXTRACT(YEAR   FROM pend-(pbegin + INTERVAL '1 microseconds'))::int4
     WHEN pFilter=TRUE  AND pPeriod='hour'      THEN EXTRACT(HOUR   FROM pend-date_trunc('hour',pbegin))::int4
     WHEN pFilter=TRUE  AND pPeriod='day'       THEN EXTRACT(DAY    FROM pend-date_trunc('day',pbegin))::int4
     WHEN pFilter=TRUE  AND pPeriod='week'      THEN EXTRACT(week   FROM pend-date_trunc('week',pbegin))::int4
     WHEN pFilter=TRUE  AND pPeriod='year'      THEN EXTRACT(YEAR   FROM pend-date_trunc('year',pbegin))::int4
     WHEN pFilter=TRUE  AND pPeriod='month'     THEN EXTRACT(MONTH  FROM pend-date_trunc('month',pbegin))::int4
     WHEN pFilter=TRUE  AND pPeriod='quarter'   THEN EXTRACT(quarter FROM pend-date_trunc('quarter',pbegin))::int4
     WHEN pFilter=TRUE  AND pPeriod='year'      THEN EXTRACT(YEAR   FROM pend-date_trunc('year',pbegin))::int4
END AS intervals
FROM
(SELECT '2020.12.26 19:00'::TIMESTAMP WITHOUT TIME zone  AS pbegin, '2020.12.27 18:00'::TIMESTAMP WITHOUT TIME zone AS pend, 'day' AS pPeriod, FALSE::bool AS pFilter) AS dddsrc
)
SELECT
CASE WHEN sbegin<pbegin THEN pbegin ELSE sbegin END AS sbegin,
CASE WHEN send>now() AND pend>now() THEN now()
     WHEN send>pend THEN pend ELSE send END AS send
FROM
(SELECT 
pbegin,
pend,
CASE WHEN pFilter=TRUE THEN date_trunc(pPeriod, pbegin) + INTERVAL '1 day' * (s) ELSE pbegin + INTERVAL '1 day' * s   END AS sbegin,
CASE WHEN pFilter=TRUE THEN date_trunc(pPeriod, pend) - INTERVAL '1 day' * (intervals - s-1)  ELSE pend - INTERVAL '1 day' * (intervals - s)  END AS send
FROM ddd, generate_series(0, ddd.intervals) AS s) AS foo
WHERE sbegin<now() AND sbegin<send