GH-46773: [GLib] Add GArrowFixedSizeListDataType

[hiroyuki-sato]

Rationale for this change

GLib should be able to use arrow::FixedSizeListType.

What changes are included in this PR?

Add GArrowFixedSizeListDataType.

Are these changes tested?

Yes.

Are there any user-facing changes?

Yes.

• GitHub Issue: [GLib] Add GArrowFixedSizeListDataType #46773

[github-actions]

⚠️ GitHub issue #46773 has been automatically assigned in GitHub to PR creator.

[Copilot]

Pull Request Overview

Adds support for FixedSizeListType in the GLib binding by introducing a new GArrowFixedSizeListDataType.

• Declare a new GArrowFixedSizeListDataType and its constructors in the header.
• Implement the new data type in the C++ binding.
• Add Ruby tests covering basic construction and string representation.

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
c_glib/arrow-glib/composite-data-type.h	Declare GArrowFixedSizeListDataType and its new_data_type/new_field functions
c_glib/arrow-glib/composite-data-type.cpp	Define and register the new type; implement the constructor methods
c_glib/test/test-fixed-size-list-data-type.rb	Add tests for FixedSizeListDataType.new, #id, #name, and #to_s

Comments suppressed due to low confidence (2)

c_glib/test/test-fixed-size-list-data-type.rb:48

• It would be helpful to add a test for list_size (e.g. assert_equal(5, @data_type.list_size)) to ensure the size is exposed correctly.

assert_equal("fixed_size_list<item: bool>[5]", @data_type.to_s)

c_glib/arrow-glib/composite-data-type.cpp:787

• The description "The size of value" is a bit vague; consider "The number of elements in each fixed-size list" for clarity.

* @list_size: The size of value.

[kou]

We should also check data_type.field.

[hiroyuki-sato]

Does this mean we need implement this method?

p data_type.field
Error: test_field(TestFixedSizeListDataType::.new): NoMethodError: undefined method 'field' for an instance of Arrow::FixedSizeListDataType

Does this mean assert_equal(Arrow::Type::BOOLEAN, @value_type.id);?

If this means We should check the item data type in the data_type, I didn't know how to get data_type from arrow::FixedSizeListType instance.

[kou]

If it doesn't exist, yes.

[kou]

This test must check whether the given field is used or not.

[hiroyuki-sato]

What do you think this change?

+      data_type = Arrow::FixedSizeListDataType.new(field, @list_size)
+      assert_equal([Arrow::Type::FIXED_SIZE_LIST, "fixed_size_list<bool_field: bool>[5]"],
+                   [data_type.id, data_type.to_s])

We can check size: 5, fileld_name: bool_field, and type: bool.

It seems FixedSizeListDataType class can't get size and type separately.

arrow/cpp/src/arrow/type_test.cc

Lines 1680 to 1698 in 57439e0

	TEST(TestFixedSizeListType, Basics) {
	std::shared_ptr<DataType> vt = std::make_shared<UInt8Type>();
	FixedSizeListType fixed_size_list_type(vt, 4);
	ASSERT_EQ(fixed_size_list_type.id(), Type::FIXED_SIZE_LIST);
	ASSERT_EQ(4, fixed_size_list_type.list_size());
	ASSERT_EQ("fixed_size_list", fixed_size_list_type.name());
	ASSERT_EQ("fixed_size_list<item: uint8>[4]", fixed_size_list_type.ToString());
	ASSERT_EQ(fixed_size_list_type.value_type()->id(), vt->id());
	ASSERT_EQ(fixed_size_list_type.value_type()->id(), vt->id());
	std::shared_ptr<DataType> st = std::make_shared<StringType>();
	std::shared_ptr<DataType> lt = std::make_shared<FixedSizeListType>(st, 3);
	ASSERT_EQ("fixed_size_list<item: string>[3]", lt->ToString());
	FixedSizeListType lt2(lt, 7);
	ASSERT_EQ("fixed_size_list<item: fixed_size_list<item: string>[3]>[7]", lt2.ToString());

[kou]

• We don't need data_type.id because data_type.to_s includes fixed_size_list.
• It's OK with #to_s in this PR but we should have readers of value_field and list_size in the future.

We can move garrow_list_data_type_get_field() to garrow_base_list_data_type_get_field() for value_field:

diff --git a/c_glib/arrow-glib/composite-data-type.cpp b/c_glib/arrow-glib/composite-data-type.cpp
index 8af1b0c862..ac5ed6809f 100644
--- a/c_glib/arrow-glib/composite-data-type.cpp
+++ b/c_glib/arrow-glib/composite-data-type.cpp
@@ -65,6 +65,25 @@ garrow_base_list_data_type_class_init(GArrowBaseListDataTypeClass *klass)
 {
 }
 
+/**
+ * garrow_base_list_data_type_get_field:
+ * @base_list_data_type: A #GArrowBaseListDataType.
+ *
+ * Returns: (transfer full): The field of value.
+ *
+ * Since: 21.0.0
+ */
+GArrowField *
+garrow_base_list_data_type_get_field(GArrowBaseListDataType *base_list_data_type)
+{
+  auto data_type = GARROW_DATA_TYPE(base_list_data_type);
+  auto arrow_data_type = garrow_data_type_get_raw(data_type);
+  auto arrow_base_list_data_type = std::static_pointer_cast<arrow::BaseListType>(arrow_data_type);
+
+  auto arrow_field = arrow_base_list_data_type->value_field();
+  return garrow_field_new_raw(&arrow_field, nullptr);
+}
+
 G_DEFINE_TYPE(GArrowListDataType, garrow_list_data_type, GARROW_TYPE_BASE_LIST_DATA_TYPE)
 
 static void
@@ -116,16 +135,14 @@ garrow_list_data_type_get_value_field(GArrowListDataType *list_data_type)
  * Returns: (transfer full): The field of value.
  *
  * Since: 0.13.0
+ *
+ * Deprecated: 21.0.0:
+ *   Use garrow_base_list_data_type_get_field() instead.
  */
 GArrowField *
 garrow_list_data_type_get_field(GArrowListDataType *list_data_type)
 {
-  auto data_type = GARROW_DATA_TYPE(list_data_type);
-  auto arrow_data_type = garrow_data_type_get_raw(data_type);
-  auto arrow_list_data_type = static_cast<arrow::ListType *>(arrow_data_type.get());
-
-  auto arrow_field = arrow_list_data_type->value_field();
-  return garrow_field_new_raw(&arrow_field, nullptr);
+  return garrow_base_list_data_type_get_field(GARROW_BASE_LIST_DATA_TYPE(list_data_type));
 }
 
 G_DEFINE_TYPE(GArrowLargeListDataType, garrow_large_list_data_type, GARROW_TYPE_DATA_TYPE)
diff --git a/c_glib/arrow-glib/composite-data-type.h b/c_glib/arrow-glib/composite-data-type.h
index de9449c41c..02de84ec50 100644
--- a/c_glib/arrow-glib/composite-data-type.h
+++ b/c_glib/arrow-glib/composite-data-type.h
@@ -38,6 +38,10 @@ struct _GArrowBaseListDataTypeClass
   GArrowDataTypeClass parent_class;
 };
 
+GARROW_AVAILABLE_IN_21_0
+GArrowField *
+garrow_base_list_data_type_get_field(GArrowBaseListDataType *base_list_data_type);
+
 #define GARROW_TYPE_LIST_DATA_TYPE (garrow_list_data_type_get_type())
 GARROW_AVAILABLE_IN_ALL
 G_DECLARE_DERIVABLE_TYPE(GArrowListDataType,

We can add garrow_fixed_size_list_data_type_get_list_size() (or list-size property) as the binding of

arrow/cpp/src/arrow/type.h

Line 1389 in 9133598

int32_t list_size() const { return list_size_; }

.

[hiroyuki-sato]

Thanks I simplified tests. I'll Create a separate PR to add garrow_base_list_data_type_get_field.

[hiroyuki-sato]

I implemented list_size property.
Shall I update this PR or create another PR?

    def setup
      @value_type = Arrow::BooleanDataType.new
      @list_size = 5
      @field_name = "bool_field"
    end

    def test_field
      field = Arrow::Field.new(@field_name, @value_type)
      data_type = Arrow::FixedSizeListDataType.new(field, @list_size)
      assert_equal(["bool_field", @value_type, @list_size],
                   [data_type.field.name,
                    data_type.field.data_type,
                    data_type.list_size])
    end

diff --git a/c_glib/arrow-glib/composite-data-type.cpp b/c_glib/arrow-glib/composite-data-type.cpp
index 035846bad1..1193ca9b42 100644
--- a/c_glib/arrow-glib/composite-data-type.cpp
+++ b/c_glib/arrow-glib/composite-data-type.cpp
@@ -67,6 +67,25 @@ garrow_base_list_data_type_class_init(GArrowBaseListDataTypeClass *klass)
 {
 }
 
+/**
+ * garrow_base_list_data_type_get_field:
+ * @base_list_data_type: A #GArrowBaseListDataType.
+ *
+ * Returns: (transfer full): The field of value.
+ *
+ * Since: 21.0.0
+ */
+GArrowField *
+garrow_base_list_data_type_get_field(GArrowBaseListDataType *base_list_data_type)
+{
+  auto data_type = GARROW_DATA_TYPE(base_list_data_type);
+  auto arrow_data_type = garrow_data_type_get_raw(data_type);
+  auto arrow_base_list_data_type = std::static_pointer_cast<arrow::BaseListType>(arrow_data_type);
+
+  auto arrow_field = arrow_base_list_data_type->value_field();
+  return garrow_field_new_raw(&arrow_field, nullptr);
+}
+
 G_DEFINE_TYPE(GArrowListDataType, garrow_list_data_type, GARROW_TYPE_BASE_LIST_DATA_TYPE)
 
 static void
@@ -118,16 +137,14 @@ garrow_list_data_type_get_value_field(GArrowListDataType *list_data_type)
  * Returns: (transfer full): The field of value.
  *
  * Since: 0.13.0
+ *
+ * Deprecated: 21.0.0:
+ *   Use garrow_base_list_data_type_get_field() instead.
  */
 GArrowField *
 garrow_list_data_type_get_field(GArrowListDataType *list_data_type)
 {
-  auto data_type = GARROW_DATA_TYPE(list_data_type);
-  auto arrow_data_type = garrow_data_type_get_raw(data_type);
-  auto arrow_list_data_type = static_cast<arrow::ListType *>(arrow_data_type.get());
-
-  auto arrow_field = arrow_list_data_type->value_field();
-  return garrow_field_new_raw(&arrow_field, nullptr);
+  return garrow_base_list_data_type_get_field(GARROW_BASE_LIST_DATA_TYPE(list_data_type));
 }
 
 G_DEFINE_TYPE(GArrowLargeListDataType, garrow_large_list_data_type, GARROW_TYPE_DATA_TYPE)
@@ -769,17 +786,55 @@ garrow_run_end_encoded_data_type_get_value_data_type(
   return garrow_data_type_new_raw(&arrow_value_data_type);
 }
 
+enum {
+  PROP_LIST_SIZE = 1
+};
+
 G_DEFINE_TYPE(GArrowFixedSizeListDataType,
               garrow_fixed_size_list_data_type,
               GARROW_TYPE_BASE_LIST_DATA_TYPE)
 
 static void
-garrow_fixed_size_list_data_type_init(GArrowFixedSizeListDataType *object)
-{
+garrow_fixed_size_list_data_type_get_property(GObject *object,
+                                              guint prop_id,
+                                              GValue *value,
+                                              GParamSpec *pspec)
+{
+  auto arrow_data_type = garrow_data_type_get_raw(GARROW_DATA_TYPE(object));
+  const auto arrow_fixed_size_list_type =
+    std::static_pointer_cast<arrow::FixedSizeListType>(arrow_data_type);
+
+  switch (prop_id) {
+  case PROP_LIST_SIZE:
+    g_value_set_int(value, arrow_fixed_size_list_type->list_size());
+    break;
+  default:
+    G_OBJECT_WARN_INVALID_PROPERTY_ID(object, prop_id, pspec);
+    break;
+  }
 }
 
 static void
 garrow_fixed_size_list_data_type_class_init(GArrowFixedSizeListDataTypeClass *klass)
+{
+  GObjectClass *gobject_class;
+  GParamSpec *spec;
+
+  gobject_class = G_OBJECT_CLASS(klass);
+  gobject_class->get_property = garrow_fixed_size_list_data_type_get_property;
+
+  spec =  g_param_spec_int("list-size",
+                           "List size",
+                           "The list size of the elements",
+                           G_MININT,
+                           G_MAXINT,
+                           0,
+                           G_PARAM_READABLE);
+  g_object_class_install_property(gobject_class, PROP_LIST_SIZE, spec);
+}
+
+static void
+garrow_fixed_size_list_data_type_init(GArrowFixedSizeListDataType *object)
 {
 }
 
diff --git a/c_glib/arrow-glib/composite-data-type.h b/c_glib/arrow-glib/composite-data-type.h
index 8369ae4987..207647bd46 100644
--- a/c_glib/arrow-glib/composite-data-type.h
+++ b/c_glib/arrow-glib/composite-data-type.h
@@ -38,6 +38,10 @@ struct _GArrowBaseListDataTypeClass
   GArrowDataTypeClass parent_class;
 };
 
+GARROW_AVAILABLE_IN_21_0
+GArrowField *
+garrow_base_list_data_type_get_field(GArrowBaseListDataType *base_list_data_type);
+
 #define GARROW_TYPE_LIST_DATA_TYPE (garrow_list_data_type_get_type())
 GARROW_AVAILABLE_IN_ALL
 G_DECLARE_DERIVABLE_TYPE(GArrowListDataType,
diff --git a/c_glib/test/test-fixed-size-list-data-type.rb b/c_glib/test/test-fixed-size-list-data-type.rb
index d8faddb9d9..9546d27405 100644
--- a/c_glib/test/test-fixed-size-list-data-type.rb
+++ b/c_glib/test/test-fixed-size-list-data-type.rb
@@ -26,20 +26,26 @@ class TestFixedSizeListDataType < Test::Unit::TestCase
     def test_field
       field = Arrow::Field.new(@field_name, @value_type)
       data_type = Arrow::FixedSizeListDataType.new(field, @list_size)
-      # TODO: check value_field and list_size separately.
-      assert_equal("fixed_size_list<bool_field: bool>[5]", data_type.to_s)
+      assert_equal(["bool_field", @value_type, @list_size],
+                   [data_type.field.name,
+                    data_type.field.data_type,
+                    data_type.list_size])
     end
 
     def test_data_type
       data_type = Arrow::FixedSizeListDataType.new(@value_type, @list_size)
-      # TODO: check value_field and list_size separately.
-      assert_equal("fixed_size_list<item: bool>[5]", data_type.to_s)
+      assert_equal(["item", @value_type, @list_size],
+                   [data_type.field.name,
+                    data_type.field.data_type,
+                    data_type.list_size])
     end
   end
 
   sub_test_case("instance_methods") do
     def setup
-      @data_type = Arrow::FixedSizeListDataType.new(Arrow::BooleanDataType.new, 5)
+      @list_size = 5
+      @value_type =Arrow::BooleanDataType.new
+      @data_type = Arrow::FixedSizeListDataType.new(@value_type, @list_size)
     end
 
     def test_name
@@ -49,5 +55,14 @@ class TestFixedSizeListDataType < Test::Unit::TestCase
     def test_to_s
       assert_equal("fixed_size_list<item: bool>[5]", @data_type.to_s)
     end
+
+    def test_list_size
+      assert_equal(@list_size, @data_type.list_size)
+    end
+
+    def test_field
+      field = Arrow::Field.new("item", @value_type)
+      assert_equal(field, @data_type.field)
+    end
   end
 end

[kou]

We can use this PR.

[hiroyuki-sato]

Thanks. I updated this PR. Please take a look when you get a chance.

[hiroyuki-sato]

Thanks. All suggested change applied.

[kou]

+1

[conbench-apache-arrow]

After merging your PR, Conbench analyzed the 3 benchmarking runs that have been run so far on merge-commit 93cae03.

There were 119 benchmark results with an error:

• Commit Run on arm64-t4g-2xlarge-linux at 2025-06-17 02:58:50Z
  • tpch (R) with engine=arrow, format=parquet, language=R, memory_map=False, query_id=TPCH-07, scale_factor=1
  • tpch (R) with engine=arrow, format=native, language=R, memory_map=False, query_id=TPCH-09, scale_factor=1
• and 117 more (see the report linked below)

There were no benchmark performance regressions. 🎉

The full Conbench report has more details.