Re: checking the gaps in intervals

Andreas Kretschmer <akretschmer@spamfence.net> wrote:

> Anton Gavazuk <antongavazuk@gmail.com> wrote:
> 
> > Hi dear community,
> > 
> > Have probably quite simple task but cannot find the solution,
> > 
> > Imagine the table A with 2 columns start and end, data type is date
> > 
> > start          end
> > 01 dec.     10 dec
> > 11 dec.     13 dec
> > 17 dec.     19 dec
> > .....
> > 
> > If I have interval, for example, 12 dec-18 dec, how can I determine
> > that the interval cannot be fully covered by values from table A
> > because of the gap 14-16 dec? Looking for solution and unfortunately
> > nothing has come to the mind yet...
> 
> I'm thinking about a solution with DATERANGE (PostgreSQL 9.2)...
> 
> 
> Are start and end including or excluding?

Okay, my solution, quick and dirty ;-)

-- that's your table:

test=*# select * from ag;date_start |  date_end  
------------+------------2012-12-01 | 2012-12-10 2012-12-11 | 2012-12-13 2012-12-17 | 2012-12-19 
(3 rows)                 



-- now some views:
test=*# \d+ view_ag;                  View "public.view_ag" Column  |   Type    | Modifiers | Storage  | Description 
----------+-----------+-----------+----------+-------------my_range | daterange |           | extended |             
View definition:                                           SELECT daterange(ag.date_start, ag.date_end, '[]'::text) AS
my_range FROM ag;
 

test=*# \d+ view_ag2;                 View "public.view_ag2" Column  |   Type    | Modifiers | Storage  | Description
----------+-----------+-----------+----------+-------------my_range | daterange |           | extended |my_lag   |
daterange|           | extended |
 
View definition:SELECT view_ag.my_range,   lag(view_ag.my_range) OVER (ORDER BY lower(view_ag.my_range)) AS my_lag
FROMview_ag;
 

test=*# \d+ view_ag3;                  View "public.view_ag3" Column   |   Type    | Modifiers | Storage  |
Description
-----------+-----------+-----------+----------+-------------my_range  | daterange |           | extended |my_lag    |
daterange|           | extended |?column?  | boolean   |           | plain    |new_range | daterange |           |
extended|
 
View definition:SELECT view_ag2.my_range, view_ag2.my_lag,   view_ag2.my_lag -|- view_ag2.my_range,       CASE
WHEN view_ag2.my_lag -|- view_ag2.my_range THEN view_ag2.my_lag + view_ag2.my_range           ELSE view_ag2.my_range
  END AS new_range  FROM view_ag2;
 

-- and now my select:
-- first case, the range is not included
test=*# select count(*) from view_ag3 where new_range @> '[2012-12-12,2012-12-18]';count
-------    0
(1 row)

-- and now, the range is included
test=*# select count(*) from view_ag3 where new_range @> '[2012-12-02,2012-12-13]';count
-------    1
(1 row)


Hope that helps, but you need the 9.2.



Andreas
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