Re: [SQL] [GENERAL] CURRENT_TIMESTAMP - Mailing list pgsql-hackers

Yes, I agree with you Manfred, but more people _don't_ want it to
change, and like it the way it is, so we will just keep it and add
now("string").

Added to TODO:

    * Add now("transaction|statement|clock") functionality

I have attached an SGML patch that explains the issues with
CURRENT_TIMESTAMP in more detail.

---------------------------------------------------------------------------

Manfred Koizar wrote:
> On Sat, 5 Oct 2002 00:29:03 -0400 (EDT), Bruce Momjian
> <pgman@candle.pha.pa.us> wrote:
> >
> >OK, are we agreed to leave CURRENT_TIMESTAMP/now() alone and just add
> >now("string")?  If no one replies, I will assume that is a yes and I
> >will add it to TODO.
>
> So my view of CURRENT_TIMESTAMP not being spec compliant didn't find
> much agreement.  No problem, such is life.
>
> May I suggest that a "Compatibility" section is added to the bottom of
> functions-datetime.html?
>
>
> In case this issue is revisited later let me add for the archives:
>
> On Fri, 04 Oct 2002 09:54:42 -0400, Tom Lane <tgl@sss.pgh.pa.us>
> wrote:
> >Freezing CURRENT_TIMESTAMP goes right along with that, and in fact makes
> >a lot of sense, because it tells you exactly what time your snapshot
> >of the database state was taken.
>
> I like this interpretation.  But bear in mind that a transaction's own
> actions are visible to later commands in the same transaction.
> Looking at the clock is an "own action", so this is perfectly
> compatible with (my reading of) General Rule 1.
>
> A statement does not see its own modifications which corresponds to
> (my interpretation of) General Rule 3.
>
> And one last thought:  There are applications out there that are not
> written for one specific database backend.  Having to replace
> CURRENT_TIMESTAMP by PG-specific now('statement') is just one more
> pain in trying to be portable across different backends.
>
> Servus
>  Manfred
>

--
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073
Index: doc/src/sgml/func.sgml
===================================================================
RCS file: /cvsroot/pgsql-server/doc/src/sgml/func.sgml,v
retrieving revision 1.126
diff -c -c -r1.126 func.sgml
*** doc/src/sgml/func.sgml    24 Sep 2002 20:14:58 -0000    1.126
--- doc/src/sgml/func.sgml    5 Oct 2002 19:00:15 -0000
***************
*** 4293,4304 ****
     </informalexample>

     <para>
!     It is quite important to realize that
!     <function>CURRENT_TIMESTAMP</function> and related functions all return
!     the time as of the start of the current transaction; their values do not
!     increment while a transaction is running.  But
!     <function>timeofday()</function> returns the actual current time.
     </para>

     <para>
      All the date/time data types also accept the special literal value
--- 4293,4309 ----
     </informalexample>

     <para>
!     It is important to realize that
!     <function>CURRENT_TIMESTAMP</function> and related functions return
!     the start time of the current transaction; their values do not
!     change during the transaction. <function>timeofday()</function>
!     returns the wall clock time and does advance during transactions.
     </para>
+
+    <note>
+     Many other database systems advance these values more
+     frequently.
+    </note>

     <para>
      All the date/time data types also accept the special literal value