mrkn commented on a change in pull request #7898:
URL: https://github.com/apache/arrow/pull/7898#discussion_r469954523
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File path: cpp/src/arrow/array/array_dict_test.cc
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@@ -904,6 +904,67 @@ TEST(TestDecimalDictionaryBuilder, DoubleTableSize) {
ASSERT_TRUE(expected.Equals(result));
}
+TEST(TestNullDictionaryBuilder, Basic) {
+ // MakeBuilder
+ auto dict_type = dictionary(int8(), null());
+ std::unique_ptr<ArrayBuilder> boxed_builder;
+ ASSERT_OK(MakeBuilder(default_memory_pool(), dict_type, &boxed_builder));
+ auto& builder = checked_cast<DictionaryBuilder<NullType>&>(*boxed_builder);
+
+ ASSERT_OK(builder.AppendNull());
+ ASSERT_OK(builder.AppendNull());
+ ASSERT_OK(builder.AppendNull());
+ ASSERT_EQ(3, builder.length());
+ ASSERT_EQ(3, builder.null_count());
+
+ ASSERT_OK(builder.AppendNulls(4));
+ ASSERT_EQ(7, builder.length());
+ ASSERT_EQ(7, builder.null_count());
+
+ auto int_array = ArrayFromJSON(int8(), "[0, 1, 0, null]");
+ ASSERT_OK(builder.AppendArray(*int_array));
Review comment:
I think this is practically meaningless. It is the same as
`AppendNulls` as its implementation. But, as `AppendArray` function in
`DictionaryBuilder` of `NullType` actually accepts an Array of any type, I
believe we should test the behavior.
We probably need to check the value type of the given `Array` in
`AppendArray`.
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