feat: implement DataWriter for Iceberg data files #552
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Implements DataWriter class for writing Iceberg data files as part of issue apache#441 (task 2). Implementation: - Factory method DataWriter::Make() for creating writer instances - Support for Parquet and Avro file formats via WriterFactoryRegistry - Complete DataFile metadata generation including partition info, column statistics, serialized bounds, and sort order ID - Proper lifecycle management with Initialize/Write/Close/Metadata - PIMPL idiom for ABI stability Tests: - 12 comprehensive unit tests covering creation, write/close lifecycle, metadata generation, error handling, and feature validation - All tests passing (12/12) Related to apache#441
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evindj
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Feb 3, 2026
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| ICEBERG_ASSIGN_OR_RAISE(writer_, | ||
| WriterFactoryRegistry::Open(options_.format, writer_options)); | ||
| return {}; |
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It is odd that an empty structure is always returned. Also, since this is initialization why not doing in the ctor?
evindj
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Feb 3, 2026
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| if (closed_) { | ||
| return InvalidArgument("Writer already closed"); | ||
| } |
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I could see a case for making close idempotent, is there any strong reason why we want to return this error instead of no op for example?
| return InvalidArgument("Writer already closed"); | ||
| } | ||
| ICEBERG_RETURN_UNEXPECTED(writer_->Close()); | ||
| closed_ = true; |
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Should this class address thread safety?
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| TEST_F(DataWriterTest, CreateWithParquetFormat) { | ||
| DataWriterOptions options{ | ||
| .path = "test_data.parquet", | ||
| .schema = schema_, | ||
| .spec = partition_spec_, | ||
| .partition = PartitionValues{}, | ||
| .format = FileFormatType::kParquet, | ||
| .io = file_io_, | ||
| .properties = {{"write.parquet.compression-codec", "uncompressed"}}, | ||
| }; | ||
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| auto writer_result = DataWriter::Make(options); | ||
| ASSERT_THAT(writer_result, IsOk()); | ||
| auto writer = std::move(writer_result.value()); | ||
| ASSERT_NE(writer, nullptr); | ||
| } | ||
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| TEST_F(DataWriterTest, CreateWithAvroFormat) { | ||
| DataWriterOptions options{ | ||
| .path = "test_data.avro", | ||
| .schema = schema_, | ||
| .spec = partition_spec_, | ||
| .partition = PartitionValues{}, | ||
| .format = FileFormatType::kAvro, | ||
| .io = file_io_, | ||
| }; | ||
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| auto writer_result = DataWriter::Make(options); | ||
| ASSERT_THAT(writer_result, IsOk()); | ||
| auto writer = std::move(writer_result.value()); | ||
| ASSERT_NE(writer, nullptr); | ||
| } |
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nit: The two tests are quite similar, it is probably possible to leverage a function to reduce duplication
| // Check length before close | ||
| auto length_result = writer->Length(); | ||
| ASSERT_THAT(length_result, IsOk()); | ||
| EXPECT_GT(length_result.value(), 0); |
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nit: check the size of the data passed to the write function?
zhjwpku
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Feb 3, 2026
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| if (!writer_) { | ||
| return InvalidArgument("Writer not initialized"); | ||
| } |
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Suggested change
| if (!writer_) { | |
| return InvalidArgument("Writer not initialized"); | |
| } | |
| ICEBERG_PRECHECK(writer_, "Writer not initialized"); |
nit, this should make the code shorter.
| } | ||
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| Result<FileWriter::WriteResult> Metadata() { | ||
| if (!closed_) { |
Collaborator
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nit: use ICEBERG_CHECK here
| EXPECT_GT(length.value(), 0); | ||
| } | ||
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| } // namespace |
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nit: move this closing namespace curly before the first TEST_F?
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Implements DataWriter class for writing Iceberg data files as part of issue #441 (task 2).
Implementation:
Related to #441