Improve signature of get_field (#10569)

datafusion/core/tests/expr_api/mod.rs

@@ -61,7 +61,7 @@ fn test_eq_with_coercion() {
 #[test]
 fn test_get_field() {
     evaluate_expr_test(
-        get_field(col("props"), lit("a")),
+        get_field(col("props"), "a"),
         vec![
             "+------------+",
             "| expr       |",
@@ -77,7 +77,7 @@ fn test_get_field() {
 #[test]
 fn test_nested_get_field() {
     evaluate_expr_test(
-        get_field(col("props"), lit("a"))
+        get_field(col("props"), "a")
             .eq(lit("2021-02-02"))
             .or(col("id").eq(lit(1))),
         vec![

datafusion/functions/src/core/mod.rs

@@ -43,7 +43,7 @@ make_udf_function!(coalesce::CoalesceFunc, COALESCE, coalesce);
 
 // Export the functions out of this package, both as expr_fn as well as a list of functions
 pub mod expr_fn {
-    use datafusion_expr::Expr;
+    use datafusion_expr::{Expr, Literal};
 
     /// returns NULL if value1 equals value2; otherwise it returns value1. This
     /// can be used to perform the inverse operation of the COALESCE expression
@@ -83,8 +83,8 @@ pub mod expr_fn {
     }
 
     /// Returns the value of the field with the given name from the struct
-    pub fn get_field(arg1: Expr, arg2: Expr) -> Expr {
-        super::get_field().call(vec![arg1, arg2])
+    pub fn get_field(arg1: Expr, field_name: impl Literal) -> Expr {
+        super::get_field().call(vec![arg1, field_name.lit()])
     }
 
     /// Returns `coalesce(args...)`, which evaluates to the value of the first expr which is not NULL