On Fri, Jul 5, 2024 at 05:03:35PM -0400, Tom Lane wrote:
> Bruce Momjian <[email protected]> writes:
> > Well, 'now()' certainly _looks_ like a function call, though it isn't.
> > The fact that 'now()'::timestamptz and 'now'::timestamptz generate
> > volatile results via a function call was my point.
>
> The only reason 'now()'::timestamptz works is that timestamptz_in
> ignores irrelevant punctuation (or what it thinks is irrelevant,
> anyway). I do not think we should include examples that look like
> that, because it will further confuse readers who don't already
> have a solid grasp of how this works.
Wow, I see that now:
test=> SELECT 'now('::timestamptz;
timestamptz
-------------------------------
2024-07-05 17:04:33.457915-04
If I remove the 'now()' mention in the docs, patch attached, I am
concerned people will be confused whether it is the removal of the
single quotes or the use of "()" which causes insert-time evaluation,
and they might try 'now()'.
--
Bruce Momjian <[email protected]> https://momjian.us
EDB https://enterprisedb.com
Only you can decide what is important to you.
diff --git a/doc/src/sgml/ref/create_table.sgml b/doc/src/sgml/ref/create_table.sgml
index f19306e7760..4d47248fccf 100644
--- a/doc/src/sgml/ref/create_table.sgml
+++ b/doc/src/sgml/ref/create_table.sgml
@@ -888,6 +888,13 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
match the data type of the column.
</para>
+ <para>
+ Note, a string that returns a volatile result once cast to a data
+ type, like <literal>'now'::timestamptz</literal>, is evaluated at
+ table creation time, while <literal>now()::timestamptz</literal>
+ (without quotes) is evaluated at data insertion time.
+ </para>
+
<para>
The default expression will be used in any insert operation that
does not specify a value for the column. If there is no default
