2009/11/22 Craig Ringer <craig@xxxxxxxxxxxxxxxxxxxxx>
On 23/11/2009 4:15 AM, Scott Marlowe wrote:I do think this comes up often enough that a built-in trigger "update
> On Sun, Nov 22, 2009 at 12:50 PM, Thom Brown <thombrown@xxxxxxxxx> wrote:
>> Hi,
>> This should be simple, but for some reason I'm not quite sure what the
>> solution is. I want to be able to update the value of a column for rows
>> that have been updated. More specifically, if a row is updated, I want it's
>> modified_date column to be populated with the current time stamp. I've
>> looked at triggers and rules, and it looks like I'd need to create a
>> function just to achieve this which seems incredibly clumsy and unnecessary.
>> Could someone enlighten me?
>
> Well, you DO have to create a function, but it's not all that clumsy
> really. Also it's quite flexible so you can do lots of complex stuff
> and hide it away in a trigger function.
named column with result of _expression_ on insert" trigger might be
desirable. Especially if implemented in C to avoid the need for PL/PgSQL
and to reduce the CPU cost a smidge.
Hmm. CC'iing -hackers; there was a discussion earlier on it being
desirable to have more "[EASY]" TODO items, and this might be a good one
for the job.
So might "CREATE LANGUAGE ... IF NOT EXISTS". Maybe even "CREATE ROLE
... IF NOT EXISTS" and "CREATE USER ... IF NOT EXISTS" - I know I'd find
them really handy.
--
Craig Ringer
I would have thought the IF NOT EXISTS syntax could be handy on every CREATE command and I wouldn't object to such a thing being implemented in future.
But my reason for the column updating on row update was due to me converting a MySQL script to PostgreSQL. MySQL had the following syntax available:
`updated_date` timestamp NOT NULL default CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP
That's effectively what I'm emulating. I think that syntax is actually quite useful. Another thing I found useful was having COMMENT available on the same line as the column declaration too. An example of this is:
`parent_id` integer unsigned NOT NULL default '0' COMMENT 'The parent menu item in the menu tree.',
I really can't think of any other syntactic sugar I'd want from MySQL though.
Thom
