The background is that the result of the day function and dates are basically the same: the number of days from the Unix epoch. When we started using metadata tables, we realized that a lot of people use the day function but then get a weird ordinal value out, but if we just change the type to `date`, engines could correctly display the value. This isn't required by the spec, it's just a convenience.
On Fri, Sep 27, 2024 at 8:30 AM Russell Spitzer <russell.spit...@gmail.com> wrote: > Good thing DateType is an Integer :) > https://github.com/apache/iceberg/blob/113c6e7d62e53d3e3cb15b1712f3a1db473ca940/api/src/main/java/org/apache/iceberg/types/Type.java#L37 > > On Thu, Sep 26, 2024 at 8:38 PM Kevin Liu <kevin.jq....@gmail.com> wrote: > >> Hey folks, >> >> While reviewing a PR to fix DayTransform in PyIceberg (#1208 >> <https://github.com/apache/iceberg-python/pull/1208>), we found an >> inconsistency between the spec and the Java Iceberg library. >> >> According to the spec >> <https://iceberg.apache.org/spec/#partition-transforms>, the result type >> for the "day partition transform" should be `int`, similar to other >> time-based partition transforms (year/month/hour). However, in the Java >> Iceberg library, the result type for day partition transform is `DateType` ( >> source >> <https://github.com/apache/iceberg/blob/dddb5f423b353d961b8a08eb2cb4371d453c2959/api/src/main/java/org/apache/iceberg/transforms/Days.java#L47>). >> This seems to be a discrepancy from the spec, as the day partition >> transform is the only time-based transform with a non-int result >> type—whereas the others use IntegerType (source >> <https://grep.app/search?q=getResultType&filter[repo][0]=apache/iceberg&filter[path][0]=api/src/main/java/org/apache/iceberg/> >> ). >> >> Could someone confirm if my understanding is correct? If so, is there any >> historical context for this difference? Lastly, how should we approach >> resolving this moving forward? >> >> Best, >> Kevin >> >>
