Re: Date_part & cast.

On Fri, 21 Apr 2000, Benoit Brodard wrote:
> Hi,
> 
> We use PostgreSQL 6.5.3 on i586-pc-linux-gnu, compiled by gcc 2.7.2.3, and we get the following results with
date_part:
 
> 
> db=> select date_part( 'dow', date '20000421' );
> date_part
> ---------
>         5
> (1 row)
> 
> db=> select date_part( 'dow', date ( '20000421' ) );
> date_part
> ---------
>         6
> (1 row)
> 
> Is this correct ?
No it is not.

> If yes, I could not find any explanation for the second result which also
> differ from "select date_part( 'dow', date (20000421)  );"

This, together with "hundreds" of other problems, has been fixed in
postgresql-7.0RC1. 

btw, the days of the week start with Sunday = 1

so your queries now say:-

template1=# select date_part( 'dow', date '20000421' );date_part
-----------        6
(1 row)
template1=# select date_part( 'dow', date ( '20000421' ) );date_part
-----------        6
(1 row)

However I think this demonstrates a bug in the date functions.

chris@berty:~ >  cal 11 1927       # In which I trust.   November 1927
Su Mo Tu We Th Fr Sa      1  2  3  4  56  7  8  9 10 11 12
13 14 15 16 17 18 19
20 21 22 23 24 25 26
27 28 29 30

template1=# select date_part( 'dow', date '19271124' );date_part
-----------        4
(1 row)             
template1=# select date_part( 'dow', date '19271125' );date_part
-----------        5
(1 row)
template1=# select date_part( 'dow', date '19271126' );date_part
-----------        0
(1 row)         

template1=# select date_part( 'dow', date '19271127' );date_part
-----------        1
(1 row)                                                                                 
There seems to be a discontinuity here doesn't there?

Using postgresql-7.0RC1.

If somebody could direct me to the general area in the source tree, I might be
able to come up with a patch & btw, to whom should I send it?

-- 
Sincerely etc.,
NAME       Christopher Sawtell - iOpen Technologies Ltd.CELL PHONE 021 257 4451ICQ UIN    45863470EMAIL      chris @
iopen. co . nz,  csawtell @ xtra . co . nzWWW        http://www.iopen.co.nzCNOTES
ftp://ftp.funet.fi/pub/languages/C/tutorials/sawtell_C.tar.gz
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