Re: Wrong manual info?

"Christopher Kings-Lynne" <chriskl(at)familyhealth(dot)com(dot)au> writes:
> As far as I can tell, 'now' works perfectly as a dynamic column DEFAULT. It
> uses insert time, NOT table creation time

Hmm. The manual is correct as written, because it warns against writing
TIMESTAMP 'now', which indeed does not work. In current sources I get:

regression=# create table foo (f1 int, f2 timestamp default TIMESTAMP 'now',
regression(# f3 timestamp default 'now');
CREATE
regression=# insert into foo values(1);
INSERT 139644 1
regression=# insert into foo values(2);
INSERT 139645 1
regression=# insert into foo values(3);
INSERT 139646 1
regression=# select * from foo;
f1 | f2 | f3
----+------------------------+------------------------
1 | 2001-10-08 10:36:02-04 | 2001-10-08 10:36:07-04
2 | 2001-10-08 10:36:02-04 | 2001-10-08 10:36:08-04
3 | 2001-10-08 10:36:02-04 | 2001-10-08 10:36:10-04
(3 rows)

regression=# \d foo
Table "foo"
Column | Type | Modifiers

--------+-----------------------------+-----------------------------------------------
f1 | integer |
f2 | timestamp(0) with time zone | default '2001-10-08 10:36:02-04'::timestamptz
f3 | timestamp(0) with time zone | default 'now'

regression=# select * from pg_attrdef where adrelid =
regression-# (select oid from pg_class where relname = 'foo');
adrelid | adnum | adbin | adsrc
---------+-------+--------------------------------------------------------------------------------------------------------------------------+---------------------------------------
139642 | 2 | { CONST :consttype 1184 :constlen 8 :constbyval false :constisnull false :constvalue 8 [ 65 -118 -93 -78 -112 0 0 0 ] } | '2001-10-08 10:36:02-04'::timestamptz
139642 | 3 | { CONST :consttype 705 :constlen -1 :constbyval false :constisnull false :constvalue 7 [ 0 0 0 7 110 111 119 ] } | 'now'
(2 rows)

So TIMESTAMP 'now' does get coerced to a timestamp constant on sight,
which is what I would expect. I find it rather surprising that the
unknown-type literal isn't getting coerced during CREATE TABLE too.
After looking at the code, I see that this is a deliberate hack to
make the world safe for DEFAULT 'now' --- see catalog/heap.c around line
1630 in current sources. However, I think this is an ugly backwards-
compatibility hack, rather than something the manual should recommend
as preferred practice. So I think the docs are okay as is.

regards, tom lane