Comments on: find overlapping time ranges

By: amnezick

amnezick — Tue, 15 Apr 2008 22:22:53 +0000

what happened to my condition?

(c>=a a.Nd c=a a.Nd d<=b)

By: amnezick

amnezick — Tue, 15 Apr 2008 22:21:41 +0000

????
what happened to my condition?
(c>=a && c=a && d

By: amnezick

amnezick — Tue, 15 Apr 2008 22:20:38 +0000

hi there. I’m trying something similar in php though and with dates. Your problem is your condition: you are missing the case (c,d) is inside (a,b). so the condition should be
(c>=a AND c=a AND d<=b) that translates into: either edges of interval (c,d) is inside interval (a,b) which is bad

By: depesz

depesz — Sat, 29 Mar 2008 13:21:09 +0000

@T1:
looks like Ants Aasma approach from his comment is the best.

By: T1

T1 — Sat, 29 Mar 2008 13:14:50 +0000

What was the final conclusion of the query?

By: depesz

depesz — Thu, 22 Nov 2007 08:56:34 +0000

@Jeff Davis:
thanks for link, i’ll definitely check it.

By: Jeff Davis

Jeff Davis — Wed, 21 Nov 2007 17:27:22 +0000

You might be interested to see the pgsql-temporal project here:

http://www.pgfoundry.org/projects/temporal/

It provides a time interval type (what you call a time range) and also provides GiST support functions so that it can be efficiently indexed, including the “overlaps” operator.

By: depesz

depesz — Wed, 21 Nov 2007 14:07:58 +0000

@Ants Aasma:
ah. sometimes the easiest approach is somehow hidden

By: depesz

depesz — Wed, 21 Nov 2007 14:01:33 +0000

@Ants Aasma:
i think the operator is missing in the “where’ clause.

but i dont really see what operator could you use to make this query return the same results as “overlaps”.

By: Ants Aasma

Ants Aasma — Wed, 21 Nov 2007 14:00:53 +0000

Stupid wordpress ate half of the criteria, meant to say
SELECT t1.*, (SELECT count(*) FROM test t2 WHERE (t2.a < t1.b AND t2.b > t1.a)) FROM test t1;

By: Ants Aasma

Ants Aasma — Wed, 21 Nov 2007 13:59:14 +0000

That or criteria simplifies as
SELECT t1.*, (SELECT count(*) FROM test t2 WHERE t2.a t1.a) FROM test t1;
This way there is one fewer index scans.