fix: downcast to FixedSizeBinaryArray in CASE bytes lookup table

datafusion/physical-expr/src/expressions/case.rs

@@ -1765,6 +1765,92 @@ mod tests {
         Ok(())
     }
 
+    #[test]
+    fn case_with_expr_fixed_size_binary() -> Result<()> {
+        let schema =
+            Schema::new(vec![Field::new("a", DataType::FixedSizeBinary(2), true)]);
+        let mut builder = FixedSizeBinaryBuilder::with_capacity(4, 2);
+        builder.append_value(b"aa")?;
+        builder.append_value(b"bb")?;
+        builder.append_null();
+        builder.append_value(b"cc")?;
+        let values = builder.finish();
+        let batch = RecordBatch::try_new(Arc::new(schema), vec![Arc::new(values)])?;
+
+        let schema = batch.schema();
+
+        // CASE a WHEN b"aa" THEN 1 WHEN b"cc" THEN 2 ELSE 3 END
+        let when1 = lit(ScalarValue::FixedSizeBinary(2, Some(b"aa".to_vec())));
+        let then1 = lit(1i32);
+        let when2 = lit(ScalarValue::FixedSizeBinary(2, Some(b"cc".to_vec())));
+        let then2 = lit(2i32);
+        let else_expr = lit(3i32);
+
+        let expr = case(
+            Some(col("a", &schema)?),
+            vec![(when1, then1), (when2, then2)],
+            Some(else_expr),
+        )?;
+        let result = expr
+            .evaluate(&batch)?
+            .into_array(batch.num_rows())
+            .expect("Failed to convert to array");
+        let result = as_int32_array(&result)?;
+
+        let expected = &Int32Array::from(vec![Some(1), Some(3), Some(3), Some(2)]);
+
+        assert_eq!(expected, result);
+
+        Ok(())
+    }
+
+    #[test]
+    fn case_with_expr_fixed_size_binary_dictionary() -> Result<()> {
+        let schema = Schema::new(vec![Field::new(
+            "a",
+            DataType::Dictionary(
+                Box::new(DataType::UInt8),
+                Box::new(DataType::FixedSizeBinary(2)),
+            ),
+            true,
+        )]);
+        let keys = UInt8Array::from(vec![0u8, 1u8, 2u8, 3u8]);
+        let mut builder = FixedSizeBinaryBuilder::with_capacity(4, 2);
+        builder.append_value(b"aa")?;
+        builder.append_value(b"bb")?;
+        builder.append_null();
+        builder.append_value(b"cc")?;
+        let values = builder.finish();
+        let dictionary = DictionaryArray::new(keys, Arc::new(values));
+        let batch = RecordBatch::try_new(Arc::new(schema), vec![Arc::new(dictionary)])?;
+
+        let schema = batch.schema();
+
+        // CASE a WHEN b"aa" THEN 1 WHEN b"cc" THEN 2 ELSE 3 END
+        let when1 = lit(ScalarValue::FixedSizeBinary(2, Some(b"aa".to_vec())));
+        let then1 = lit(1i32);
+        let when2 = lit(ScalarValue::FixedSizeBinary(2, Some(b"cc".to_vec())));
+        let then2 = lit(2i32);
+        let else_expr = lit(3i32);
+
+        let expr = case(
+            Some(col("a", &schema)?),
+            vec![(when1, then1), (when2, then2)],
+            Some(else_expr),
+        )?;
+        let result = expr
+            .evaluate(&batch)?
+            .into_array(batch.num_rows())
+            .expect("Failed to convert to array");
+        let result = as_int32_array(&result)?;
+
+        let expected = &Int32Array::from(vec![Some(1), Some(3), Some(3), Some(2)]);
+
+        assert_eq!(expected, result);
+
+        Ok(())
+    }
+
     // Make sure we are not failing when got literal in case when but input is dictionary encoded
     #[test]
     fn case_with_expr_boolean_dictionary() -> Result<()> {

datafusion/physical-expr/src/expressions/case/literal_lookup_table/bytes_like_lookup_table.rs

@@ -106,7 +106,9 @@ fn try_get_bytes_iterator(
 
         DataType::LargeBinary => Box::new(array.as_binary::<i64>().into_iter()),
 
-        DataType::FixedSizeBinary(_) => Box::new(array.as_binary::<i64>().into_iter()),
+        DataType::FixedSizeBinary(_) => {
+            Box::new(array.as_fixed_size_binary().into_iter())
+        }
 
         DataType::Utf8View => Box::new(
             array

datafusion/sqllogictest/test_files/case.slt

@@ -836,6 +836,63 @@ NULL 0 0 0 0 0
 63 0 0 0 0 0
 64 3 3 3 3 3
 
+# CASE with FixedSizeBinary WHEN literals (regression test for #26012)
+query ?II
+select
+    letter_binary as letter
+    ,CASE letter_fsb
+        WHEN arrow_cast(X'62', 'FixedSizeBinary(1)') THEN 1
+        WHEN arrow_cast(X'61', 'FixedSizeBinary(1)') THEN 2
+        WHEN arrow_cast(X'64', 'FixedSizeBinary(1)') THEN 3
+        ELSE 0
+    END as fsb_literals
+    ,CASE arrow_cast(letter_fsb, 'Dictionary(Int32, FixedSizeBinary(1))')
+        WHEN arrow_cast(X'62', 'FixedSizeBinary(1)') THEN 1
+        WHEN arrow_cast(X'61', 'FixedSizeBinary(1)') THEN 2
+        WHEN arrow_cast(X'64', 'FixedSizeBinary(1)') THEN 3
+        ELSE 0
+    END as fsb_dict_literals
+FROM letters_binary;
+----
+61 2 2
+62 1 1
+NULL 0 0
+63 0 0
+61 2 2
+63 0 0
+64 3 3
+
+# Minimal reproducer for issue #26012
+query I
+SELECT CASE x
+         WHEN arrow_cast(X'01', 'FixedSizeBinary(1)') THEN 1
+         WHEN arrow_cast(X'02', 'FixedSizeBinary(1)') THEN 2
+         ELSE 3
+       END AS r
+FROM (SELECT arrow_cast(X'03', 'FixedSizeBinary(1)') AS x);
+----
+3
+
+query I
+SELECT CASE x
+         WHEN arrow_cast(X'01', 'FixedSizeBinary(1)') THEN 1
+         WHEN arrow_cast(X'02', 'FixedSizeBinary(1)') THEN 2
+         ELSE 3
+       END AS r
+FROM (SELECT arrow_cast(X'01', 'FixedSizeBinary(1)') AS x);
+----
+1
+
+query I
+SELECT CASE x
+         WHEN arrow_cast(X'01', 'FixedSizeBinary(1)') THEN 1
+         WHEN arrow_cast(X'02', 'FixedSizeBinary(1)') THEN 2
+         ELSE 3
+       END AS r
+FROM (SELECT arrow_cast(X'02', 'FixedSizeBinary(1)') AS x);
+----
+2
+
 statement ok
 drop table source;