diff --git a/native/core/src/execution/datafusion/expressions/mod.rs b/native/core/src/execution/datafusion/expressions/mod.rs
index 2bb14df36..5f9f322b2 100644
--- a/native/core/src/execution/datafusion/expressions/mod.rs
+++ b/native/core/src/execution/datafusion/expressions/mod.rs
@@ -23,7 +23,6 @@ use crate::errors::CometError;
 pub mod bloom_filter_agg;
 pub mod bloom_filter_might_contain;
 pub mod negative;
-pub mod strings;
 pub mod subquery;
 pub mod unbound;
 
diff --git a/native/core/src/execution/datafusion/planner.rs b/native/core/src/execution/datafusion/planner.rs
index 5e77b3f65..0e64ed6af 100644
--- a/native/core/src/execution/datafusion/planner.rs
+++ b/native/core/src/execution/datafusion/planner.rs
@@ -25,12 +25,8 @@ use crate::{
         datafusion::{
             expressions::{
                 bloom_filter_agg::BloomFilterAgg,
-                bloom_filter_might_contain::BloomFilterMightContain,
-                checkoverflow::CheckOverflow,
-                negative,
-                strings::{Contains, EndsWith, Like, StartsWith, StringSpaceExpr, SubstringExpr},
-                subquery::Subquery,
-                unbound::UnboundColumn,
+                bloom_filter_might_contain::BloomFilterMightContain, checkoverflow::CheckOverflow,
+                negative, subquery::Subquery, unbound::UnboundColumn,
             },
             operators::expand::CometExpandExec,
             shuffle_writer::ShuffleWriterExec,
@@ -90,9 +86,10 @@ use datafusion_comet_proto::{
     spark_partitioning::{partitioning::PartitioningStruct, Partitioning as SparkPartitioning},
 };
 use datafusion_comet_spark_expr::{
-    ArrayInsert, Avg, AvgDecimal, BitwiseNotExpr, Cast, Correlation, Covariance, CreateNamedStruct,
-    DateTruncExpr, GetArrayStructFields, GetStructField, HourExpr, IfExpr, ListExtract, MinuteExpr,
-    NormalizeNaNAndZero, RLike, SecondExpr, SparkCastOptions, Stddev, SumDecimal,
+    ArrayInsert, Avg, AvgDecimal, BitwiseNotExpr, Cast, Contains, Correlation, Covariance,
+    CreateNamedStruct, DateTruncExpr, EndsWith, GetArrayStructFields, GetStructField, HourExpr,
+    IfExpr, Like, ListExtract, MinuteExpr, NormalizeNaNAndZero, RLike, SecondExpr,
+    SparkCastOptions, StartsWith, Stddev, StringSpaceExpr, SubstringExpr, SumDecimal,
     TimestampTruncExpr, ToJson, Variance,
 };
 use datafusion_common::scalar::ScalarStructBuilder;
diff --git a/native/core/src/execution/kernels/mod.rs b/native/core/src/execution/kernels/mod.rs
index 675dcd489..d72dd4060 100644
--- a/native/core/src/execution/kernels/mod.rs
+++ b/native/core/src/execution/kernels/mod.rs
@@ -19,5 +19,3 @@
 
 mod hash;
 pub use hash::hash;
-
-pub(crate) mod strings;
diff --git a/native/spark-expr/src/kernels/mod.rs b/native/spark-expr/src/kernels/mod.rs
index 88aa34b1a..3669ff13a 100644
--- a/native/spark-expr/src/kernels/mod.rs
+++ b/native/spark-expr/src/kernels/mod.rs
@@ -17,4 +17,5 @@
 
 //! Kernels
 
+pub mod strings;
 pub(crate) mod temporal;
diff --git a/native/core/src/execution/kernels/strings.rs b/native/spark-expr/src/kernels/strings.rs
similarity index 96%
rename from native/core/src/execution/kernels/strings.rs
rename to native/spark-expr/src/kernels/strings.rs
index d63b2c477..bb275fbb9 100644
--- a/native/core/src/execution/kernels/strings.rs
+++ b/native/spark-expr/src/kernels/strings.rs
@@ -25,15 +25,14 @@ use arrow::{
     compute::kernels::substring::{substring as arrow_substring, substring_by_char},
     datatypes::{DataType, Int32Type},
 };
-
-use crate::errors::ExpressionError;
+use datafusion_common::DataFusionError;
 
 /// Returns an ArrayRef with a string consisting of `length` spaces.
 ///
 /// # Preconditions
 ///
 /// - elements in `length` must not be negative
-pub fn string_space(length: &dyn Array) -> Result<ArrayRef, ExpressionError> {
+pub fn string_space(length: &dyn Array) -> Result<ArrayRef, DataFusionError> {
     match length.data_type() {
         DataType::Int32 => {
             let array = length.as_any().downcast_ref::<Int32Array>().unwrap();
@@ -52,7 +51,7 @@ pub fn string_space(length: &dyn Array) -> Result<ArrayRef, ExpressionError> {
     }
 }
 
-pub fn substring(array: &dyn Array, start: i64, length: u64) -> Result<ArrayRef, ExpressionError> {
+pub fn substring(array: &dyn Array, start: i64, length: u64) -> Result<ArrayRef, DataFusionError> {
     match array.data_type() {
         DataType::LargeUtf8 => substring_by_char(
             array
diff --git a/native/spark-expr/src/lib.rs b/native/spark-expr/src/lib.rs
index 15f446ef3..5dff6e0b8 100644
--- a/native/spark-expr/src/lib.rs
+++ b/native/spark-expr/src/lib.rs
@@ -33,6 +33,8 @@ mod correlation;
 pub use correlation::Correlation;
 mod covariance;
 pub use covariance::Covariance;
+mod strings;
+pub use strings::{Contains, EndsWith, Like, StartsWith, StringSpaceExpr, SubstringExpr};
 mod kernels;
 mod list;
 mod regexp;
diff --git a/native/core/src/execution/datafusion/expressions/strings.rs b/native/spark-expr/src/strings.rs
similarity index 99%
rename from native/core/src/execution/datafusion/expressions/strings.rs
rename to native/spark-expr/src/strings.rs
index 200b4ec5a..a8aab6aee 100644
--- a/native/core/src/execution/datafusion/expressions/strings.rs
+++ b/native/spark-expr/src/strings.rs
@@ -17,7 +17,7 @@
 
 #![allow(deprecated)]
 
-use crate::execution::kernels::strings::{string_space, substring};
+use crate::kernels::strings::{string_space, substring};
 use arrow::{
     compute::{
         contains_dyn, contains_utf8_scalar_dyn, ends_with_dyn, ends_with_utf8_scalar_dyn, like_dyn,