FromPostgres returns a Volatility that matches the postgres provolatile/proleakproof settings.

Immutable means that the operator cannot modify the database, the transaction state, or any other state.

Leakproof means that the operator cannot modify the database, the transaction state, or any other state.

Stable means that the operator cannot modify the database or the transaction state and is guaranteed to return the same results given the same arguments whenever it is evaluated within the same statement.

Volatile means that the operator can do anything, including modifying database state.

V indicates whether the result of a function is dependent *only* on the values of its explicit arguments, or can change due to outside factors (such as parameter variables or table contents).