Hello,
A question from a complete newbie on this area.
I'm trying to implement a mechanism that would allow me to keep track of the last time each row of a table was modified.
I have many applications modifying the data, and I would like to avoid having to modify each of those applications (with the risk of forgetting one of them).
So, I figured a better approach would be a trigger that gets activated on update (before update, to be specific).
Below is what I came up with, but being the very first time I do (or even read about) something with triggers or with plpgsql, I'd like to check if there are any obvious red flags, or if what I'm doing is hopelessly wrong.
I added a column last_modified (timestamp data type), and create the following function:
create function set_last_modified() returns trigger as ' begin new.last_modified = now(); return new; end; ' language plpgsql;
(this is similar to an example from the PG documentation; I'm not sure the keyword "new" is the right thing to use in my case, but it would look like it's a standard way to refer to the "new row" that is about to replace the old one)
Then, I created the trigger as follows:
create trigger last_modified_on_update before update on table_name for each row execute procedure set_last_modified();
The thing seems to work -- I had to go in a shell as user postgres and execute the command:
$ createlang -d dbname plpgsql
(I'm not sure I understand why that is necessary, or what implications -- positive or negative -- it may have)
Am I doing the right thing? Have I introduced some sort of catastrophe waiting to happen?
Thanks for any guidance you may offer to this PL/PGSQL beginner!
Carlos --
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