Beautiful piece of code =)

Nice code

I would expect a boolean to be returned by a function called "is_hit" - not a string

calculator(1, 2, 'import("os").system("rm -rf /")')
eval will run this... gotta be carefull with eval!

SUM in postgress while adding float/numeric colum should automatically return a float value

The PostgresSQL docs have sum ( numeric ) → numeric