PG Bug reporting form <noreply@postgresql.org> writes:
> SET timestampCol = $1 + interval '1 minute';
> ...results in an error...
> ERROR: column "timestampcol" is of type timestamp without time zone but
> expression is of type interval
> LINE 4: set timestampCol = $1 + interval '1 minute';
> ^
As in your other report, the context in which the parameter type is
guessed is just the immediate context of the plus-operator expression.
The relevant rule there is "guess that an unknown input is of the same
type as the other input", so we resolve the operator as interval + interval.
regards, tom lane