From: Jasen Betts <jasen@xnet.co.nz>
To: pgsql-sql@postgresql.org
Subject: Re: SQL to Check whether "AN HOUR PERIOD" is between start and end timestamps
Date: 10 Apr 2009 22:41:54 GMT
Message-ID: <grohvi$f4t$1@reversiblemaps.ath.cx> (raw)
References: <19947.64230.qm@web94606.mail.in2.yahoo.com>
<49BFBC61.9020006@archonet.com>
<849335.93192.qm@web27903.mail.ukl.yahoo.com>
<20090402135404.GD3163@alvh.no-ip.org>
On 2009-04-02, Alvaro Herrera <alvherre@commandprompt.com> wrote:
> James Kitambara wrote:
>> Dear Srikanth,
>> You can solve your problem by doing this
>>
>> THE SQL IS AS FOLLOWS
>> ASSUME TIME INTERVAL 2008-12-07 07:59:59 TO 2008-12-07 08:58:59 AND THE TABLE NAME time_interval
>>
>> COUNT (*) FROM
>> (select customer_id, log_session_id, start_ts, end_ts , end_ts-start_ts as "Interval" from time_interval
>> where end_ts-start_ts >= '1 hour'
>> and '2008-12-07 07:59:59' between start_ts and end_ts)
>> AS COUNT ;
>
> Another way to phrase the WHERE clause is with the OVERLAPS operator,
> something like this:
>
> WHERE (start_ts, end_ts) OVERLAPS ('2008-12-07 07:59:59', '2008-12-07 08:59:59')
>
> What I'm not so sure about is how optimizable this construct is.
>
http://www.postgresql.org/docs/8.3/interactive/xindex.html
if you gave the apropriate GIST index on (start_ts, end_ts) the
overlaps may be optimisable. the subquery will run to completion
and count will count the results. - but this form gives different results.
beter to do
select COUNT (*) AS COUNT FROM time_interval
WHERE (start_ts, end_ts) OVERLAPS ('2008-12-07 07:59:59', '2008-12-07 08:59:59')
or
select COUNT (*) AS COUNT FROM time_interval
where end_ts-start_ts >= '1 hour'
and '2008-12-07 07:59:59' between start_ts and end_ts;
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To: pgsql-sql@postgresql.org
Cc: jasen@xnet.co.nz
Subject: Re: SQL to Check whether "AN HOUR PERIOD" is between start and end timestamps
In-Reply-To: <grohvi$f4t$1@reversiblemaps.ath.cx>
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