fix: result type of DayTransform should be date #285
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Result type of Day transform should be `int` per the spec, but in the Java impl, it is `DateType`, this discrepancy has been discussed on devlist, see [1]. iceberg-iceberg and iceberg-rust all conform to the java impl, so make iceberg-cpp do the same. The added comments are borrowed from iceberg-python. [1] https://lists.apache.org/thread/2gq7b54nvc9q6f1j08l9lnzgm5onkmx5
shangxinli
reviewed
Nov 2, 2025
| {.str = "day", | ||
| .source_type = iceberg::timestamp(), | ||
| .expected_result_type = iceberg::int32()}, | ||
| .expected_result_type = iceberg::date()}, |
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Adding tests for Wire Format Compatibility would be better. The PR changes the return type from int32() to date() but doesn't verify:
- That date() values serialize to int32 on the wire
- That existing partitioned data files can still be read
- That this change is backward compatible with tables partitioned using the old int32 type
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I'm afraid we don't have fully covered integration test yet. I added a test for PartitionSpec, though I'm not sure if that's sufficient.
wgtmac
approved these changes
Nov 3, 2025
gty404
approved these changes
Nov 3, 2025
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Result type of Day transform should be
intper the spec, but in the Java impl, it isDateType, this discrepancy has been discussed on devlist, see [1]. iceberg-iceberg and iceberg-rust all conform to the java impl, so make iceberg-cpp do the same.The added comments are borrowed from iceberg-python.
[1] https://lists.apache.org/thread/2gq7b54nvc9q6f1j08l9lnzgm5onkmx5