Minor: fix signature fn octect_length() (#10726)

* fix: signature fn octect_length

* chore: add test

Author: marvinlanhenke

datafusion/core/tests/expr_api/mod.rs

@@ -28,6 +28,23 @@ use std::sync::{Arc, OnceLock};
 
 mod simplification;
 
+#[test]
+fn test_octet_length() {
+    #[rustfmt::skip]
+    evaluate_expr_test(
+        octet_length(col("list")),
+        vec![
+            "+------+",
+            "| expr |",
+            "+------+",
+            "| 5    |",
+            "| 18   |",
+            "| 6    |",
+            "+------+",
+        ],
+    );
+}
+
 #[test]
 fn test_eq() {
     // id = '2'

datafusion/functions/src/string/mod.rs

@@ -128,8 +128,8 @@ pub mod expr_fn {
     }
 
     #[doc = "returns the number of bytes of a string"]
-    pub fn octet_length(args: Vec<Expr>) -> Expr {
-        super::octet_length().call(args)
+    pub fn octet_length(args: Expr) -> Expr {
+        super::octet_length().call(vec![args])
     }
 
     #[doc = "replace the substring of string that starts at the start'th character and extends for count characters with new substring"]