emkornfield commented on a change in pull request #10729:
URL: https://github.com/apache/arrow/pull/10729#discussion_r671403080
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File path: cpp/src/parquet/arrow/arrow_reader_writer_test.cc
##########
@@ -3796,6 +3796,95 @@ TEST(TestArrowWriterAdHoc, SchemaMismatch) {
ASSERT_RAISES(Invalid, writer->WriteTable(*tbl, 1));
}
+// ----------------------------------------------------------------------
+// Tests for directly writing DictionaryArray
+class TestArrowWriteDictionary : public ::testing::Test {
+ public:
+ void SetUp() override {
+ properties_ = default_arrow_writer_properties();
+ serialized_data_ = AllocateBuffer();
+ }
+
+ // Generates a range of single character strings from start to end
(inclusive)
+ // Nulls will be inserted starting at index 0. If there are any null
+ // values then start will not be the true min. However, the dictionary
+ // array will always contain all the values even if they aren't all used.
+ void GenerateRange(int num_nulls, char start, char end) {
+ int num_values = end - start + 1;
+ DCHECK_LT(num_nulls, num_values);
+
+ ::arrow::StringBuilder dictionary_builder;
+ ::arrow::Int32Builder indices_builder;
+
+ for (char val = start; val <= end; val++) {
+ int32_t index = static_cast<int32_t>(val - start);
+ if (val - start >= num_nulls) {
+ ASSERT_OK(indices_builder.Append(index));
+ } else {
+ ASSERT_OK(indices_builder.AppendNull());
+ }
+ ASSERT_OK(dictionary_builder.Append(&val, 1));
+ }
+
+ std::shared_ptr<::arrow::Array> dictionary;
+ std::shared_ptr<::arrow::Array> indices;
+ ASSERT_OK(dictionary_builder.Finish(&dictionary));
+ ASSERT_OK(indices_builder.Finish(&indices));
+
+ ASSERT_OK_AND_ASSIGN(auto test_column,
+ ::arrow::DictionaryArray::FromArrays(indices,
dictionary));
+
+ auto schema = ::arrow::schema({::arrow::field("values",
test_column->type())});
+ auto batch = ::arrow::RecordBatch::Make(schema, num_values, {test_column});
+ ASSERT_OK_AND_ASSIGN(test_data_,
::arrow::Table::FromRecordBatches({batch}));
+ }
+
+ void WriteToBuffer() {
+ auto out_stream =
std::make_shared<::arrow::io::BufferOutputStream>(serialized_data_);
+ auto writer_properties = default_writer_properties();
+ std::unique_ptr<FileWriter> writer;
+ ASSERT_OK(FileWriter::Open(*test_data_->schema(),
::arrow::default_memory_pool(),
+ out_stream, writer_properties,
+ default_arrow_writer_properties(), &writer));
+ ASSERT_OK(writer->WriteTable(*test_data_,
std::numeric_limits<int64_t>::max()));
+ ASSERT_OK(writer->Close());
+ }
+
+ std::shared_ptr<FileMetaData> LoadWrittenMetadata() {
+ auto buffer_reader =
std::make_shared<::arrow::io::BufferReader>(serialized_data_);
+ auto parquet_reader = ParquetFileReader::Open(std::move(buffer_reader));
+ return parquet_reader->metadata();
+ }
+
+ void CheckNullCount() {
+ GenerateRange(5, 'a', 'z');
+ WriteToBuffer();
+ auto metadata = LoadWrittenMetadata();
+ auto stats = metadata->RowGroup(0)->ColumnChunk(0)->statistics();
+ ASSERT_TRUE(stats->HasNullCount());
+ ASSERT_EQ(stats->null_count(), 5);
+ ASSERT_EQ(stats->num_values(), 21);
+ }
+
+ void CheckMinMax() {
+ GenerateRange(5, 'a', 'z');
+ WriteToBuffer();
+ auto metadata = LoadWrittenMetadata();
Review comment:
Please generally careful with the use of auto. The [style guide
recommends it just of saving
space](https://google.github.io/styleguide/cppguide.html#Type_deduction)
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