Обсуждение: Fastest way / best practice to calculate "next birthdays"

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

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/2007/10/26/who-has-birthday-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/2007/10/26/who-has-birthday-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/

Hannes Dorbath wrote:

> Sorry, I think I phrased the question badly. What I'm after basically is:
>
> http://www.depesz.com/index.php/2007/10/26/who-has-birthday-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

If I have to find upcoming birthdays in current week and the current week
fall into different months - how would you handle that?





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If I have to find upcoming birthdays in current week and the current week
fall into different months - how would you handle that?

On 05/20/15 20:22, David G. Johnston wrote:
> On Monday, May 18, 2015, er.tejaspatel88@gmail.com <
> er.tejaspatel88@gmail.com> wrote:
>
>> If I have to find upcoming birthdays in current week and the current week
>> fall into different months - how would you handle that?
>>
>
> Extract(week from timestamptz_column)
>
> ISO weeks are not affected by month boundaries but do start on Monday.

There is the year start/end boundary conditions to worry about there.

If the current week covers Dec28-Jan02 then week of year won't help for
a birthday on Jan01 or Jan02 if 'today' is in the Dec portion.  Ditto
for birthday in Dec portion when 'today' is in the Jan portion.

There is probably a better way to do it than what I'm showing here, but
here's an example:

with x as (
   select now() - (extract(dow from now()) || ' days')::interval as
weekstart
)
select to_char(x.weekstart, 'YYYY-MM-DD') as first_day,
        to_char(x.weekstart + '6 days', 'YYYY-MM-DD') as last_day
    from x;

You could probably make some of that into a function that accepts a
timestamptz and generates the two days.  Or even does the compare too.

HTH.

Bosco.

On 05/20/15 20:22, David G. Johnston wrote:
> On Monday, May 18, 2015, er.tejaspatel88@gmail.com <
> er.tejaspatel88@gmail.com> wrote:
>
>> If I have to find upcoming birthdays in current week and the current week
>> fall into different months - how would you handle that?
>>
>
> Extract(week from timestamptz_column)
>
> ISO weeks are not affected by month boundaries but do start on Monday.

There is the year start/end boundary conditions to worry about there.

If the current week covers Dec28-Jan02 then week of year won't help for
a birthday on Jan01 or Jan02 if 'today' is in the Dec portion.  Ditto
for birthday in Dec portion when 'today' is in the Jan portion.

On 5/21/15 11:15 AM, Bosco Rama wrote:
> You could probably make some of that into a function that accepts a
> timestamptz and generates the two days.

You'll be better off if instead of 2 days it gives you a daterange:
http://www.postgresql.org/docs/9.4/static/rangetypes.html

I don't know about the exact ISO details, but your approach is the
correct one: find the date that the current week started on and then
build a range of [week start, week start + 7 days).

Also, note the use of [ vs ). That is the ONLY correct way to do this if
you're comparing to a timestamp.
--
Jim Nasby, Data Architect, Blue Treble Consulting
Data in Trouble? Get it in Treble! http://BlueTreble.com

"er.tejaspatel88@gmail.com" <er.tejaspatel88@gmail.com> wrote:

> If I have to find upcoming birthdays in current week and the
> current week fall into different months - how would you handle
> that?

If you don't need to cross from December into January, I find the
easiest is:

SELECT * FROM person
  WHERE (EXTRACT(MONTH FROM dob), EXTRACT(DAY FROM dob))
          BETWEEN (6, 28) AND (7, 4);

That is logicically the same as:

SELECT * FROM person
  WHERE (EXTRACT(MONTH FROM dob) >= 6
    AND (EXTRACT(MONTH FROM dob) > 6
     OR (EXTRACT(DAY FROM dob) >= 28)))
    AND (EXTRACT(MONTH FROM dob) <= 7
    AND (EXTRACT(MONTH FROM dob) < 7
     OR (EXTRACT(DAY FROM dob) <= 4)));

That's the generalized case; with the months adjacent, this simpler
form is also equivalent:

SELECT * FROM person
  WHERE (EXTRACT(MONTH FROM dob) = 6
    AND EXTRACT(DAY FROM dob) >= 28)
    OR (EXTRACT(MONTH FROM dob) = 7
    AND EXTRACT(DAY FROM dob) <= 4);

The first query I showed is faster than either of the alternatives,
especially if there is an index on dob.

--
Kevin Grittner
EDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company