The subject basically says it all, I'm looking for the fastest
(indexable) way to calculate the next birthdays relative to NOW() from a
dataset of about 1 million users.

I'm currently using a function based index, but leap year handling /
mapping February 29 to February 28 gives me some headaches.

Is there any best practice to do that in PostgreSQL?


--
Best regards,
Hannes Dorbath

Hannes Dorbath wrote:
> The subject basically says it all, I'm looking for the fastest
> (indexable) way to calculate the next birthdays relative to NOW() from a
> dataset of about 1 million users.
>
> I'm currently using a function based index, but leap year handling /
> mapping February 29 to February 28 gives me some headaches.
>
> Is there any best practice to do that in PostgreSQL?

postgres=# SELECT current_date|| ' a ' || to_char(current_date, 'Day'),

current_date + '1 Year'::interval || ' a ' || to_char(current_date + '1
Year'::interval, 'Day') as next_birthday;
?column? | next_birthday
------------------------+---------------------------------
2008-05-04 a Sunday | 2009-05-04 00:00:00 a Monday

?


Sincerely,

Joshua D. Drake


--
Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-performance

Joshua D. Drake wrote:
> postgres=# SELECT current_date|| ' a ' || to_char(current_date, 'Day'),
> current_date + '1 Year'::interval || ' a ' || to_char(current_date + '1
> Year'::interval, 'Day') as next_birthday;
> ?column? | next_birthday
> ------------------------+---------------------------------
> 2008-05-04 a Sunday | 2009-05-04 00:00:00 a Monday
>
> ?

Sorry, I think I phrased the question badly. What I'm after basically is:

http://www.depesz.com/index.php/2007...hday-tomorrow/


--
Best regards,
Hannes Dorbath

Hannes Dorbath írta:
> Joshua D. Drake wrote:
>> postgres=# SELECT current_date|| ' a ' || to_char(current_date, 'Day'),
>> current_date + '1 Year'::interval || ' a ' || to_char(current_date +
>> '1 Year'::interval, 'Day') as next_birthday;
>> ?column? | next_birthday
>> ------------------------+---------------------------------
>> 2008-05-04 a Sunday | 2009-05-04 00:00:00 a Monday
>>
>> ?
>
> Sorry, I think I phrased the question badly. What I'm after basically is:
>
> http://www.depesz.com/index.php/2007...hday-tomorrow/

If you define the same functional index as in the above link:

CREATE OR REPLACE FUNCTION indexable_month_day(date) RETURNS TEXT as $BODY$
SELECT to_char($1, 'MM-DD');
$BODY$ language 'sql' IMMUTABLE STRICT;

create table user_birthdate (
id serial not null primary key,
birthdate date
);
create index user_birthdate_day_idx on user_birthdate (
indexable_month_day(birthdate) );

Then you can use this query:

select count(*) from user_birthdate where indexable_month_day(birthdate)
> '02-28' and indexable_month_day(birthdate) <= '03-01';

In a generic and parametrized way:

select * from user_birthdate
where
indexable_month_day(birthdate) > indexable_month_day(now()::date) and
indexable_month_day(birthdate) <= indexable_month_day((now() + '1
days'::interval)::date);

This will still use the index and it will work for the poor ones
who have birthday every 4 years, too. Assume, it's 02-08 today, 03-01
the next day.
The now() < X <= now() + 1 day range will find 02-29.

--
----------------------------------
Zoltán Böszörményi
Cybertec Schönig & Schönig GmbH
http://www.postgresql.at/



--
Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-performance

Hannes Dorbath wrote:

> Sorry, I think I phrased the question badly. What I'm after basically is:
>
> http://www.depesz.com/index.php/2007...hday-tomorrow/
>

OK So what I came up with is - (the times are from a G4 1.25Ghz)

CREATE TABLE birthdaytest
(
id serial PRIMARY KEY,
birthdate date
);


CREATE INDEX idx_bday_month ON birthdaytest
USING btree(extract(month from birthdate));

CREATE INDEX idx_bday_day ON birthdaytest
USING btree(extract(day from birthdate));


insert into birthdaytest (birthdate) values
('1930-01-01'::date+generate_series(0,365*70));

.... I repeated this another 15 times to load some data


vacuum analyse birthdaytest;

\timing

select count(*) from birthdaytest;

> count
> --------
> 408816
> (1 row)
>
> Time: 233.501 ms


select * from birthdaytest
where extract(month from birthdate) = 5
and extract(day from birthdate) between 6 and 12;

> id | birthdate
> --------+------------
> 126 | 1930-05-06
> 127 | 1930-05-07
> 128 | 1930-05-08
> ...
> ...
> 408613 | 1999-05-11
> 408614 | 1999-05-12
> (7840 rows)
>
> Time: 211.237 ms


select * from birthdaytest
where extract(month from birthdate) = extract(month from current_date)
and extract(day from birthdate) between extract(day from current_date)
and extract(day from current_date+14);

> id | birthdate
> --------+------------
> 125 | 1930-05-05
> 126 | 1930-05-06
> 127 | 1930-05-07
> ...
> ...
> 408619 | 1999-05-17
> 408620 | 1999-05-18
> 408621 | 1999-05-19
> (16800 rows)
>
> Time: 483.915 ms


--

Shane Ambler
pgSQL (at) Sheeky (dot) Biz

Get Sheeky @ http://Sheeky.Biz

--
Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-performance