On 12/07/2014 12:11 PM, Sérgio Saquetim wrote:
I've noticed a strange behavior in the generate_series functions.
I'm trying to get all days between a start and an end date including the
bounds. So naturally I've tried something like the query below
.
The real query uses generate_series to join other tables and is much
more complicated, but for the sake of brevity, I think that this query
is good enough to show the problem.
:
postgres=# SELECT generate_series('2014-10-10'::DATE,
'2014-10-15'::DATE, '1 DAY'::INTERVAL);
generate_series
------------------------
2014-10-10 00:00:00-03
2014-10-11 00:00:00-03
2014-10-12 00:00:00-03
2014-10-13 00:00:00-03
2014-10-14 00:00:00-03
2014-10-15 00:00:00-03
(6 rows)
Please note that the upper bound
'2014-10-15' is included in the resulting rows.
Now if I try this same query with slightly different dates I get:
postgres=# SELECT generate_series('2014-10-15'::DATE,
'2014-10-20'::DATE, '1 DAY'::INTERVAL);
generate_series
------------------------
2014-10-15 00:00:00-03
2014-10-16 00:00:00-03
2014-10-17 00:00:00-03
2014-10-18 00:00:00-03
2014-10-19 01:00:00-02
(5 rows)
-----------------------------------------------
The upper bound is not included in the results!
-----------------------------------------------
Here, in Brazil our DST started on Oct 19. So if I had to guess I would
say that this strange behavior is due to the DST, but I'm having a hard
time to understand why this is happening!
Is this expected behavior?
I know that I can achieve the results I expect with the following query:
postgres=# WITH RECURSIVE days(d) AS (
SELECT '2014-10-15'::DATE
UNION ALL
SELECT d+1 FROM days WHERE d < '2014-10-20'::DATE
)
SELECT * FROM days;
d
------------
2014-10-15
2014-10-16
2014-10-17
2014-10-18
2014-10-19
2014-10-20
(6 rows)
But using that instead of generate_series, just feels wrong so I would
like to understand what's happening and if there is a way to overcome
that, before changing my queries.
First generate_series is really looking for a timestamp on input and
returns timestamps:
http://www.postgresql.org/docs/9.3/interactive/functions-srf.html
generate_series(start, stop, step interval) timestamp or timestamp with
time zone setof timestamp or setof timestamp with time zone (same as
argument type) Generate a series of values, from start to stop with a
step size of step
So:
test=# set timezone='Brazil/East';
SET
test=# SELECT generate_series('2014-10-10'::TIMESTAMP,
'2014-10-20'::TIMESTAMP, '1 DAY'::INTERVAL);
generate_series
---------------------
2014-10-10 00:00:00
2014-10-11 00:00:00
2014-10-12 00:00:00
2014-10-13 00:00:00
2014-10-14 00:00:00
2014-10-15 00:00:00
2014-10-16 00:00:00
2014-10-17 00:00:00
2014-10-18 00:00:00
2014-10-19 00:00:00
2014-10-20 00:00:00
test=# SELECT generate_series('2014-10-10'::TIMESTAMP WITH TIME ZONE,
'2014-10-20'::TIMESTAMP WITH TIME ZONE, '1 DAY'::INTERVAL);
generate_series
------------------------
2014-10-10 00:00:00-03
2014-10-11 00:00:00-03
2014-10-12 00:00:00-03
2014-10-13 00:00:00-03
2014-10-14 00:00:00-03
2014-10-15 00:00:00-03
2014-10-16 00:00:00-03
2014-10-17 00:00:00-03
2014-10-18 00:00:00-03
2014-10-19 01:00:00-02
Though this part I do not understand:
test=# select '2014-10-19'::timestamp with time zone;
timestamptz
------------------------
2014-10-19 01:00:00-02
(1 row)
test=# select '2014-10-20'::timestamp with time zone;
timestamptz
------------------------
2014-10-20 00:00:00-02
(1 row)
I thought interval understood 23/25 'day' across DST/ST boundaries. I
will have to think more on this.
Thank you!
Sérgio Saquetim
--
Adrian Klaver
adrian.klaver@xxxxxxxxxxx
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