fix SPARK-48498

Author: wForget

native/spark-expr/src/static_invoke/char_varchar_utils/read_side_padding.rs

@@ -18,7 +18,7 @@
 use crate::utils::make_scalar_function;
 use arrow::array::builder::GenericStringBuilder;
 use arrow::array::types::Int32Type;
-use arrow::array::{Array, AsArray};
+use arrow::array::{as_dictionary_array, make_array, Array, AsArray, DictionaryArray};
 use arrow::array::{ArrayRef, OffsetSizeTrait};
 use arrow::datatypes::DataType;
 use datafusion::common::{cast::as_generic_string_array, DataFusionError};
@@ -56,6 +56,25 @@ fn spark_read_side_padding2(
             DataType::LargeUtf8 => {
                 spark_read_side_padding_space_internal::<i64>(array, truncate, array_int)
             }
+            // Dictionary support required for SPARK-48498
+            DataType::Dictionary(_, value_type) => {
+                let dict = as_dictionary_array::<Int32Type>(array);
+                let values = if value_type.as_ref() == &DataType::Utf8 {
+                    spark_read_side_padding_space_internal::<i32>(
+                        dict.values(),
+                        truncate,
+                        array_int,
+                    )?
+                } else {
+                    spark_read_side_padding_space_internal::<i64>(
+                        dict.values(),
+                        truncate,
+                        array_int,
+                    )?
+                };
+                let result = DictionaryArray::try_new(dict.keys().clone(), values)?;
+                Ok(make_array(result.into()))
+            }
             other => Err(DataFusionError::Internal(format!(
                 "Unsupported data type {other:?} for function rpad/read_side_padding",
             ))),