Accept local timestamps annotated with the legacy timestamp types
- Langage dominant
- Java
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Description
The rules for TIMESTAMP forward-compatibility were created based on the assumption that TIMESTAMP_MILLIS and TIMESTAMP_MICROS have only been used in the instant aka. UTC-normalized semantics so far.
From this false premise it followed that TIMESTAMPs with local semantics were a new type and did not need to be annotated with the old types to maintain compatibility. In fact, annotating them with the old types were considered to be harmful, since it would have mislead older readers into thinking that they can read TIMESTAMPs with local semantics, when in reality they would have misinterpreted them as TIMESTAMPs with instant semantics. This would have lead to a difference of several hours, corresponding to the time zone offset.
In reality, however, this misinterpretation of timestamps has already been going on for a while, since Arrow annotates local timestamps with TIMESTAMP_MILLIS or TIMESTMAP_MICROS.
To maintain forward compatibilty of local timestamps, Arrow annotates them with the legacy timestamp logical types. However, the Java library considers these logical types to be incompatible and discards the new type in favour of the legacy ones (since doing the other way around would change the behaviour). Parquet-mr should be updated so that it accepts this combination of new and old logical types.
**Reporter**: [Zoltan Ivanfi](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=zi) / @zivanfi
**Assignee**: [Nándor Kollár](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=nkollar) / @nandorKollar
#### PRs and other links:
- [Discussion on the mailing list](https://lists.apache.org/thread.html/04b9a8a156939adae1aa4cf2d4e3abd2137f541cbf92ade6d775dc06@%3Cdev.parquet.apache.org%3E)
**Note**: *This issue was originally created as [PARQUET-1628](https://issues.apache.org/jira/browse/PARQUET-1628). Please see the [migration documentation](https://issues.apache.org/jira/browse/PARQUET-2502) for further details.*
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Piste de recherche
Lisez d’abord l’issue et la discussion liée de la liste de diffusion, puis suivez la gestion par parquet-java des types logiques d’horodatage et les vérifications de compatibilité de la bibliothèque Java. Confirmez le comportement des horodatages locaux d’Arrow annotés avec TIMESTAMP_MILLIS ou TIMESTAMP_MICROS ; le travail est considéré comme terminé lorsque cette combinaison est acceptée sans supprimer le nouveau type.
Rédigé par le modèle d'indexation à partir du texte de l'issue.
Évaluation
- Stack technique
- java
- Domaine
- data-engineering
- Type d'issue
- Bug
- Difficulté
- 4/5
- Temps estimé
- 3-5 jours
- Activité
- À l'abandon
- Clarté
- Plutôt claire
- Accessibilité débutants
- 35/100