presto-main/src/main/java/io/prestosql/util/SpatialJoinUtils.java/SpatialJoinUtils/getFunctionName
class SpatialJoinUtils:    private static String getFunctionName(FunctionCall functionCall)
    {
        return ResolvedFunction.fromQualifiedName(functionCall.getName())
                .map(ResolvedFunction::getSignature)
                .map(Signature::getName)
                .orElse(functionCall.getName().toString());
    }