I read thru your info, thanks a lot.
In fact, I only need to decide whether a table (the whole) has been updated
since last query. I have some pulldown menus in a VB app which extract data
from a remote site with slow connection. And the data in those tables for
pulldowns changes rarely. So if the pulldown has to extract the data and
transmit it thru slow connection, the pulldown will take a few seconds to be
in action, which is a little bit annoying, especially if the data is the
same as in the array of client. So if I can query the table, knowing that no
data changed in the table since my last query, I can use the client side
array as pulldown data without waiting for long transmition time.
I wonder if there is some more direct method, or thru the pg system tables
to get this info. If there's not out there, I would use a trigger which will
update a seperate table containing the last update time of all tables (not
records) for pulldowns.
-Jason
----- Original Message -----
From: "Richard Huxton" <dev@archonet.com>
To: "pg" <pg@newhonest.com>; <pgsql-general@postgresql.org>
Sent: Friday, December 05, 2003 5:53 PM
Subject: Re: [GENERAL] last update time of a table
> On Friday 05 December 2003 01:21, pg wrote:
> > Is there any simple way to query the most recent time of "changes" made
to
> > a table?
> >
> > I'm accessing my database with ODBC to a remote site thru internet. I
want
> > to eliminate some DUPLICATE long queries by evaluating whether the data
has
> > been
> > changed since last query. What should I do?
>
> The canonical way is to add a last_changed column and a trigger to make
sure
> it gets updated whenever the rest of the row is.
>
> Go over to http://techdocs.postgresql.org/ and check in the plpgsql
cookbook
> or my Postgresql notes, or the archives come to think of it.
>
> --
> Richard Huxton
> Archonet Ltd
>
> ---------------------------(end of broadcast)---------------------------
> TIP 9: the planner will ignore your desire to choose an index scan if your
> joining column's datatypes do not match
>
