On 09.02.23 10:11, Pavel Stehule wrote: > first and main (for me) - I can use psql variables tab complete - just > :B<tab> - it is significantly faster > second - I can see all connection related information by \set > third - there is not hook on reconnect in psql - so if you implement > BACKEND_PID by self, you ensure to run query with pg_backend_pid() after > any reconnect or connection change. > > It is clean so you can run "select pg_backend_pid() AS "BACKEND_PID" > \gset" and you can store it to .psqlrc. But most of the time I am in > customer's environment, and I have the time, possibility to do a > complete setup of .psqlrc. It looks (for me) like a generally useful > feature to be everywhere.
But what do you need the backend PID for in the first place?
Of course, you might want to use it to find your own session in pg_stat_activity or something like that, but then you're already in a query and can use pg_backend_pid(). What do you need the backend PID for outside of such a query?
In every real use case you can use pg_backend_pid(), but you need to write a complete name without tab complete, and you need to know so this function is available.
BACKEND_PID is supported by tab complete, and it is displayed in \set list and \? variables. Nothing less, nothing more, Custom psql variable can have some obsolete value.
I can imagine using :BACKEND_PID in \echo command - and it just saves you one step with its own custom variable.
It is just some more comfort with almost zero cost.
