Sargable Custom Functions in Queries

[David Allen]

Is there any way to enforce a custom function to be Sargable with a query? I've run multiple tests, and even with a simple function that returns a static number, it seems to take 2x as long as hardcoding the number of putting it in a Variable.

For example, doing a query that has a qualifier like:

WHERE table.column = 4

Is of course the fastest with indexing.

WHERE table.column = variable (which =4)

Is the same speed.

BUT WHERE table.column = DETERMINISTIC FUNCTION RESULT (4)

Takes 2x+ longer.

This seems ridiculous to me as functions are a critical part of complex SQL queries.

Is there any way to have MySQL treat a function call as a sargable application against a query?