fix: allow Binary type coercion in split_part function

Author: lemorage

datafusion/functions/src/string/split_part.rs

@@ -24,7 +24,9 @@ use arrow::array::{AsArray, GenericStringBuilder};
 use arrow::datatypes::DataType;
 use datafusion_common::ScalarValue;
 use datafusion_common::cast::as_int64_array;
-use datafusion_common::types::{NativeType, logical_int64, logical_string};
+use datafusion_common::types::{
+    NativeType, logical_binary, logical_int64, logical_string,
+};
 use datafusion_common::{DataFusionError, Result, exec_datafusion_err, exec_err};
 use datafusion_expr::{
     Coercion, ColumnarValue, Documentation, TypeSignatureClass, Volatility,
@@ -66,8 +68,16 @@ impl SplitPartFunc {
         Self {
             signature: Signature::coercible(
                 vec![
-                    Coercion::new_exact(TypeSignatureClass::Native(logical_string())),
-                    Coercion::new_exact(TypeSignatureClass::Native(logical_string())),
+                    Coercion::new_implicit(
+                        TypeSignatureClass::Native(logical_string()),
+                        vec![TypeSignatureClass::Native(logical_binary())],
+                        NativeType::String,
+                    ),
+                    Coercion::new_implicit(
+                        TypeSignatureClass::Native(logical_string()),
+                        vec![TypeSignatureClass::Native(logical_binary())],
+                        NativeType::String,
+                    ),
                     Coercion::new_implicit(
                         TypeSignatureClass::Native(logical_int64()),
                         vec![TypeSignatureClass::Integer],

datafusion/sqllogictest/test_files/binary.slt

@@ -311,3 +311,27 @@ Foo foo Foo foo
 NULL NULL NULL NULL
 Bar Bar Bar Bar
 FooBar fooBar FooBar fooBar
+
+# implicit coercion from Binary to String
+query TTT
+SELECT
+  cast(binary as varchar) as str,
+  split_part(binary, 'o', 2) as binary_split,
+  split_part(largebinary, 'o', 2) as large_binary_split
+from t;
+----
+Foo (empty) (empty)
+NULL NULL NULL
+Bar (empty) (empty)
+FooBar (empty) (empty)
+
+query T
+SELECT split_part('abc~@~def~@~ghi', arrow_cast('~@~', 'Binary'), 2);
+----
+def
+
+# Reproducer for https://github.com/apache/datafusion/issues/19809
+query T
+SELECT split_part(split_part(arrow_cast('page.html?resolution=1920&more', 'Binary'), 'resolution=', 2), '&', 1);
+----
+1920