removed un-needed ut8 check

Author: Rich-T-kid

datafusion/physical-plan/src/aggregates/group_values/single_group_by/dictionary.rs

@@ -49,12 +49,11 @@ macro_rules! decode_list {
                         if len == -1 {
                             builder.values().append_null();
                         } else {
-                            let s = std::str::from_utf8(
-                                &raw_vector[offset..offset + len as usize],
-                            )
-                            .map_err(|e| {
-                                Internal(format!("Invalid utf8 in list element: {e}"))
-                            })?;
+                            let s = unsafe {
+                                std::str::from_utf8_unchecked(
+                                    &raw_vector[offset..offset + len as usize],
+                                )
+                            };
                             builder.values().append_value(s);
                             offset += len as usize;
                         }
@@ -72,9 +71,7 @@ macro_rules! decode_scalar_string {
         for raw_bytes in $raw {
             match raw_bytes {
                 Some(raw_vector) => {
-                    let s = std::str::from_utf8(raw_vector).map_err(|e| {
-                        Internal(format!("Invalid utf8 in GroupValuesDictionary: {e}"))
-                    })?;
+                    let s = unsafe { std::str::from_utf8_unchecked(raw_vector) };
                     builder.append_value(s);
                 }
                 None => builder.append_null(),