Question

I have a Postgres database (9) that I am writing a trigger for. I want the trigger to set the modification time, and user id for a record. In Firebird you have a CONNECTIONID that you can use in a trigger, so you could add a value to a table when you connect to the database (this is a desktop application, so connections are persistent for the lifetime of the app), something like this:

UserId | ConnectionId
---------------------
544    | 3775

and then look up in the trigger that connectionid 3775 belongs to userid 544 and use 544 as the user that modified the record.

Is there anything similar I can use in Postgres?

Answer 1

you could use the process id. It can be retrieved with:

pg_backend_pid()

With this pid you can also use the table pg_stat_activity to get more information about the current backend, althouht you already should know everything, since you are using this backend.

Or better. Just create a serial, and retrieve one value from it for each connection:

CREATE SEQUENCE 'connectionids';

And then:

SELECT next_val('connectionids');

in each connection, to retrieve a connection unique id.