Function project_schema 

pub fn project_schema(
    schema: &SchemaRef,
    projection: Option<&Vec<usize>>,
) -> Result<SchemaRef>

Applies an optional projection to a SchemaRef, returning the projected schema

Example:

use arrow::datatypes::{DataType, Field, Schema, SchemaRef};
use datafusion_common::project_schema;

// Schema with columns 'a', 'b', and 'c'
let schema = SchemaRef::new(Schema::new(vec![
    Field::new("a", DataType::Int32, true),
    Field::new("b", DataType::Int64, true),
    Field::new("c", DataType::Utf8, true),
]));

// Pick columns 'c' and 'b'
let projection = Some(vec![2, 1]);
let projected_schema = project_schema(&schema, projection.as_ref()).unwrap();

let expected_schema = SchemaRef::new(Schema::new(vec![
    Field::new("c", DataType::Utf8, true),
    Field::new("b", DataType::Int64, true),
]));

assert_eq!(projected_schema, expected_schema);