I wouldn't put in the DROP option. Or at least not in that form of syntax.
By convention CREATE persists DDL and makes object definitions visible across sessions. DECLARE defines session private objects which cannot collide with other sessions.
If you want variables with a short lifetime that get dropped at the end of the transaction that by definition would imply a session private object. So it ought to be DECLARE'd.
As far as I can see PG has been following this practice so far.
I am thinking so there is little bit overlap between DECLARE and CREATE TEMP VARIABLE command. With DECLARE command, you are usually has not any control when variable will be destroyed. For CREATE TEMP xxxx is DROP IF EXISTS, but it should not be used.
It should be very similar to our current temporary tables, that are created in session related temp schema.
I can imagine, so DECLARE command will be introduced as short cut for CREATE TEMP VARIABLE, but in this moment I would not to open this topic. I afraid of bikeshedding and I hope so CREATE TEMP VAR is anough.
