diff --git a/datafusion/functions/src/string/common.rs b/datafusion/functions/src/string/common.rs
index 0d1f90eb22b94..6e5f767013d4c 100644
--- a/datafusion/functions/src/string/common.rs
+++ b/datafusion/functions/src/string/common.rs
@@ -61,7 +61,7 @@ pub(crate) fn general_trim<T: OffsetSizeTrait>(
                 str::trim_start_matches::<&[char]>(input, pattern.as_ref());
             // `ltrimmed_str` is actually `input`[start_offset..],
             // so `start_offset` = len(`input`) - len(`ltrimmed_str`)
-            let start_offset = input.as_bytes().len() - ltrimmed_str.as_bytes().len();
+            let start_offset = input.len() - ltrimmed_str.len();
 
             (ltrimmed_str, start_offset as u32)
         },
@@ -78,7 +78,7 @@ pub(crate) fn general_trim<T: OffsetSizeTrait>(
                 str::trim_start_matches::<&[char]>(input, pattern.as_ref());
             // `btrimmed_str` can be got by rtrim(ltrim(`input`)),
             // so its `start_offset` should be same as ltrim situation above
-            let start_offset = input.as_bytes().len() - ltrimmed_str.as_bytes().len();
+            let start_offset = input.len() - ltrimmed_str.len();
             let btrimmed_str =
                 str::trim_end_matches::<&[char]>(ltrimmed_str, pattern.as_ref());
 
diff --git a/datafusion/functions/src/unicode/strpos.rs b/datafusion/functions/src/unicode/strpos.rs
index 1917cd7291cc2..5d1986e44c92a 100644
--- a/datafusion/functions/src/unicode/strpos.rs
+++ b/datafusion/functions/src/unicode/strpos.rs
@@ -173,13 +173,13 @@ where
                 // the sub vector in the main vector. This is faster than string.find() method.
                 if ascii_only {
                     // If the substring is empty, the result is 1.
-                    if substring.as_bytes().is_empty() {
+                    if substring.is_empty() {
                         T::Native::from_usize(1)
                     } else {
                         T::Native::from_usize(
                             string
                                 .as_bytes()
-                                .windows(substring.as_bytes().len())
+                                .windows(substring.len())
                                 .position(|w| w == substring.as_bytes())
                                 .map(|x| x + 1)
                                 .unwrap_or(0),