This repository was archived by the owner on Jan 28, 2021. It is now read-only.
This repository was archived by the owner on Jan 28, 2021. It is now read-only.
Proposal: Specify function arity instead of using reflection #37
Description
Current state
Right now, we pass a interface{} as the UDF, which then is inspected and called using reflect.
Proposal
Instead, I propose to have fixed arity specified by the user.
Benefits of this:
- does not use reflection, so more maintainable code
- just looking at the registry you can see the arity of the function
- does not allow random signatures, so it's more type-safe
The implementation would look like the following:
type Function interface {
Arity() int
}
type Function1 func(sql.Expression) sql.Expression
type Function2 func(sql.Expression, sql.Expression) sql.Expression)
// ...
type FunctionN func(sql.Expression, sql.Expression, sql.Expression, sql.Expression) sql.Expression)
func (Function1) Arity() int { return 1 }
func (Function2) Arity() int { return 2 }
// ...
func (FunctionN) Arity() int { return n }
// Call could be converted to Call(...sql.Expression)
func Call(fn Function, exprs ...sql.Expression) (sql.Expression, error) {
if fn.Arity() != len(exprs) { /* throw error */ }
switch fn := fn.(type) {
case Function1: fn(exprs[0])
// ...
}
}Then in the registry:
var Functions = map[string]Function{
"func": Function1(NewMyFunc),
}