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Re: Absolute value of intervals

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Joshua Berry wrote:
I couldn't find the operator '@' for intervals and found this thread
from over six years ago:
http://archives.postgresql.org/pgsql-general/2003-09/msg00292.php

| "Claudio Lapidus" <clapidus@xxxxxxxxxxx> writes:
| > Bruce Momjian wrote:
| >> Why would you want an abolute value of a negative interval?
|
| > Because I'm trying to match pairs of records that satisfy certain criteria,
|
| Given that we have a unary-minus operator for intervals, I see no
| conceptual objection to having an absolute-value operator (and \do shows
| that interval is the only standard datatype that has the former but not
| the latter).
|
| However, given that it doesn't seem to be a really widely useful
| operator, I think this is the kind of itch that you'll have to scratch
| yourself.  Send us a patch and it'll get into the next release ...
|
| 			regards, tom lane

Is this is the case now? I have some data that is related but requires
fuzzy joining on timestamps within a time interval.

I'd like to be able to do this:
select * from enviados e, recibidos r where  @ (e.fecha - r.fecha) <
interval '1 second'

rather than this:
select * from enviados e, recibidos r where  (e.fecha - r.fecha) <
interval '1 second' AND (r.fecha - e.fecha) <  interval '1 second'

or this:
select * from enviados e, recibidos r where (r.fecha + interval '1
seconds', r.fecha - interval '1 seconds') OVERLAPS (e.fecha, e.fecha);

If such an operator doesn't exist yet, I'm keen to try to generate a
patch and tests; but I could use some pointers as to which project
files that should be related to such a change.

Regards,
-Joshua Berry


You should test for a positive or negative interval against INTERVAL '0 seconds' because you can have a positive interval that is a fraction of a second.

But we've got two projects that implement a period data type, pgTemporal and Chronos.
http://pgfoundry.org/projects/temporal/
http://pgfoundry.org/projects/timespan/

Scott Bailey

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