Обсуждение: Passing parameters to a Trigger
I need to pass to a trigger two dynamic text parameters stored into a
table (I can obtain them via a simple select). How can I obtain such a
thing?
Thanks everyone,
Antonio Scotti
Antonio, > I need to pass to a trigger two dynamic text parameters stored into a > table (I can obtain them via a simple select). How can I obtain such a > thing? You can't. Triggers do not accept parameters. If the parameters you're talking about are table columns, you can access them through the NEW and OLD record objects. -- -Josh Berkus Aglio Database Solutions San Francisco
Triggers do accept parameters. In fact when you type CREATE TRIGGER you can also specify some arguments. They are accessible via trigdata not by the standard args of a function (in fact a trigger function must not have parameters). The manual makes an example of passing the current_user to a trigger, but it is not clear to me. Can anyone explain how to make it works? Antonio Scotti Josh Berkus ha scritto: >Antonio, > > > >>I need to pass to a trigger two dynamic text parameters stored into a >>table (I can obtain them via a simple select). How can I obtain such a >>thing? >> >> > >You can't. Triggers do not accept parameters. > >If the parameters you're talking about are table columns, you can access them >through the NEW and OLD record objects. > > >
Antonio Scotti <ascotti@mbigroup.it> writes:
> The manual makes an example of passing the
> current_user to a trigger, but it is not clear to me.
Where exactly? I couldn't find any such example in a quick search.
In general, the arguments offered in CREATE TRIGGER can only be literal
constants, so I don't think this could work.
regards, tom lane
The exact reference to what I've read is: in the .pdf file
"programmer-7.2-A4.pdf" at the very beginning of page 240. It is the
programmer's reference manual, the section regardings the CREATE TRIGGER
command in the paragraph explaing the meaning of 'args'.
It says something about passing the current_user to a trigger but it
is not clear to me so I'd like to have it explained.
However I've managed to solve my problem in another way. I simply
call the trigger with no parameters at all and then I do a query into
the trigger body (which is written in C) so I get the missing parameters.
Regards,
Antonio Scotti
Tom Lane ha scritto:
>Antonio Scotti <ascotti@mbigroup.it> writes:
>
>
>>The manual makes an example of passing the
>>current_user to a trigger, but it is not clear to me.
>>
>>
>
>Where exactly? I couldn't find any such example in a quick search.
>
>In general, the arguments offered in CREATE TRIGGER can only be literal
>constants, so I don't think this could work.
>
> regards, tom lane
>
>
Antonio Scotti <ascotti@mbigroup.it> writes:
> The exact reference to what I've read is: in the .pdf file
> "programmer-7.2-A4.pdf" at the very beginning of page 240. It is the
> programmer's reference manual, the section regardings the CREATE TRIGGER
> command in the paragraph explaing the meaning of 'args'.
> It says something about passing the current_user to a trigger but it
> is not clear to me so I'd like to have it explained.
No, what it's suggesting is passing two field names (constant strings)
to a trigger, which then uses those as the names of the fields to stick
current user and current time values into. The trigger would have to
compute current user and current time for itself.
regards, tom lane
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