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.
Thanks a lot!
------------------ Original ------------------
From: "Laurenz Albe";<laurenz.a...@cybertec.at>;
Send time: Monday, May 7, 2018 3:57 PM
To: "a"<372660...@qq.com>; "pgsql-general"<pgsql-gene...@postgresql.org>;
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
