Allow using dictionary arrays as filters

datafusion/core/tests/dataframe/mod.rs

@@ -29,7 +29,10 @@ use arrow::{
     },
     record_batch::RecordBatch,
 };
-use arrow_array::{Array, Float32Array, Float64Array, UnionArray};
+use arrow_array::{
+    Array, BooleanArray, DictionaryArray, Float32Array, Float64Array, Int8Array,
+    UnionArray,
+};
 use arrow_buffer::ScalarBuffer;
 use arrow_schema::{ArrowError, UnionFields, UnionMode};
 use datafusion_functions_aggregate::count::count_udaf;
@@ -2363,3 +2366,105 @@ async fn dense_union_is_null() {
     ];
     assert_batches_sorted_eq!(expected, &result_df.collect().await.unwrap());
 }
+
+#[tokio::test]
+async fn boolean_dictionary_as_filter() {
+    let values = vec![Some(true), Some(false), None, Some(true)];
+    let keys = vec![0, 0, 1, 2, 1, 3, 1];
+    let values_array = BooleanArray::from(values);
+    let keys_array = Int8Array::from(keys);
+    let array =
+        DictionaryArray::new(keys_array, Arc::new(values_array) as Arc<dyn Array>);
+    let array = Arc::new(array);
+
+    let field = Field::new(
+        "my_dict",
+        DataType::Dictionary(Box::new(DataType::Int8), Box::new(DataType::Boolean)),
+        true,
+    );
+    let schema = Arc::new(Schema::new(vec![field]));
+
+    let batch = RecordBatch::try_new(schema, vec![array.clone()]).unwrap();
+
+    let ctx = SessionContext::new();
+
+    ctx.register_batch("dict_batch", batch).unwrap();
+
+    let df = ctx.table("dict_batch").await.unwrap();
+
+    // view_all
+    let expected = [
+        "+---------+",
+        "| my_dict |",
+        "+---------+",
+        "| true    |",
+        "| true    |",
+        "| false   |",
+        "|         |",
+        "| false   |",
+        "| true    |",
+        "| false   |",
+        "+---------+",
+    ];
+    assert_batches_eq!(expected, &df.clone().collect().await.unwrap());
+
+    let result_df = df.clone().filter(col("my_dict")).unwrap();
+    let expected = [
+        "+---------+",
+        "| my_dict |",
+        "+---------+",
+        "| true    |",
+        "| true    |",
+        "| true    |",
+        "+---------+",
+    ];
+    assert_batches_eq!(expected, &result_df.collect().await.unwrap());
+
+    // test nested dictionary
+    let keys = vec![0, 2]; // 0 -> true, 2 -> false
+    let keys_array = Int8Array::from(keys);
+    let nested_array = DictionaryArray::new(keys_array, array);
+
+    let field = Field::new(
+        "my_nested_dict",
+        DataType::Dictionary(
+            Box::new(DataType::Int8),
+            Box::new(DataType::Dictionary(
+                Box::new(DataType::Int8),
+                Box::new(DataType::Boolean),
+            )),
+        ),
+        true,
+    );
+
+    let schema = Arc::new(Schema::new(vec![field]));
+
+    let batch = RecordBatch::try_new(schema, vec![Arc::new(nested_array)]).unwrap();
+
+    ctx.register_batch("nested_dict_batch", batch).unwrap();
+
+    let df = ctx.table("nested_dict_batch").await.unwrap();
+
+    // view_all
+    let expected = [
+        "+----------------+",
+        "| my_nested_dict |",
+        "+----------------+",
+        "| true           |",
+        "| false          |",
+        "+----------------+",
+    ];
+
+    assert_batches_eq!(expected, &df.clone().collect().await.unwrap());
+
+    let result_df = df.clone().filter(col("my_nested_dict")).unwrap();
+    let expected = [
+        "+----------------+",
+        "| my_nested_dict |",
+        "+----------------+",
+        "| true           |",
+        "+----------------+",
+    ];
+
+    assert_batches_eq!(expected, &result_df.collect().await.unwrap());
+}

datafusion/expr/src/logical_plan/plan.rs

@@ -2102,6 +2102,17 @@ impl Filter {
         Self::try_new_internal(predicate, input, true)
     }
 
+    fn is_allowed_filter_type(data_type: &DataType) -> bool {
+        match data_type {
+            // Interpret NULL as a missing boolean value.
+            DataType::Boolean | DataType::Null => true,
+            DataType::Dictionary(_, value_type) => {
+                Filter::is_allowed_filter_type(value_type.as_ref())
+            }
+            _ => false,
+        }
+    }
+
     fn try_new_internal(
         predicate: Expr,
         input: Arc<LogicalPlan>,
@@ -2112,8 +2123,7 @@ impl Filter {
         // construction (such as with correlated subqueries) so we make a best effort here and
         // ignore errors resolving the expression against the schema.
         if let Ok(predicate_type) = predicate.get_type(input.schema()) {
-            // Interpret NULL as a missing boolean value.
-            if predicate_type != DataType::Boolean && predicate_type != DataType::Null {
+            if !Filter::is_allowed_filter_type(&predicate_type) {
                 return plan_err!(
                     "Cannot create filter with non-boolean predicate '{predicate}' returning {predicate_type}"
                 );