I would like to add some auditing triggers to PG, to log all changes to tables. I have found an example trigger ( wiki.postgresql.com – 9.1+ audit trigger ), which gets me started.
What I would like to do is pass along some additional data automatically, such as the user-id
or other key, so that the trigger can link the change back to the application user that made it. The basic flow would go like this:
- Get a connection for the current request
- Run custom SQL to set a context variable (
set conn_context = {userid};
) - Read / parse that variable inside the trigger
- Write the value to a log table along with the other information
When using MS SQL I was able to execute a statement that set the context for the connection by executing SET CONTEXT_INFO ...data...
. I am hoping there is a way to do this for PG; I haven't found one yet, but that may just be bad google-fu.
Best Answer
Old question, but still valid, so here is what I ended up using.
On 9.6 and above, to set the values either of the following will work:
select set_config('app.userid', '3', true)
SET LOCAL "app.userid" = 3;
(or'3'
)To read the value out,
select current_value('app.userid')
I ended up wrapping the lookup for the userid or other field in a function, to handle the type conversion(s) and the fact that it might not be set: