On 05/07/2018 01:39 AM, a wrote:
Thank you for your reply;
Please allow me to ask few more questions:
1, Since I'm writing a C trigger function, is there any method for me to
get some of the basic information like the follow:
(1) Total number of rows;
(2) Rows' names;
(3) Value of OLD and NEW;
2, Is there any possibility of passing the SQL statement it self into
the trigger?
3, Is it possible for me to exam before statement trigger so that I
would be able to loop it once and copying the update information to the
rest of rows.
Transition table(s):
https://www.postgresql.org/docs/10/static/sql-createtrigger.html
This is new to version 10 and I have not actually used this feature yet,
so all I can do is point you at the docs.
Thanks a lot!
------------------ Original ------------------
*From: * "Laurenz Albe";<laurenz.albe@xxxxxxxxxxx>;
*Send time:* Monday, May 7, 2018 3:57 PM
*To:* "a"<372660931@xxxxxx>; "pgsql-general"<pgsql-general@xxxxxxxxxxxxxx>;
*Subject: * Re: Is it possible to get username information while
writingtrigger?
a wrote:
> What I want is to add a log entry at the last column of each row,
which will record the
> history update, insert automatically when relative statement is
processed.
>
> I have read the documentation on triggers, which helps a lot.
However, I may have few
> more extra requirement to complete my wishes:
>
> 1, I would like to get the username of who executed the statement;
>
> 2, I would like to get the column name that is being updated;
>
> If it is possible and how should I do it??
You could use the "current_user" function to get the current user.
Mind, however, that updates caused by a cascading update from a
foreign key constraint will be executed as the owner of the table,
so it would be better to use "session_user" to avoid surprises.
You cannot get the column name, because PostgreSQL updates a whole row,
not an individual column. The best you can do is to check which
column values are different in OLD and NEW.
Yours,
Laurenz Albe
--
Cybertec | https://www.cybertec-postgresql.com
--
Adrian Klaver
adrian.klaver@xxxxxxxxxxx
