apache / apache/parquet-java

Accept local timestamps annotated with the legacy timestamp types

Abierto
#1,562 0 comentarios 0 reacciones 0 asignados Ver en GitHub
Component: Java Component: Parquet Priority: Major Type: task
Lenguaje dominante
Java
Estrellas
3.1k
Forks
1.6k
Merge medio
3 d 12 h
PR fusionados (30 d)
33

Descripción

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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Línea de trabajo

Lee primero el issue y la discusión vinculada de la lista de correo, y luego sigue el tratamiento que hace parquet-java de los tipos lógicos de marca de tiempo y las comprobaciones de compatibilidad de la biblioteca Java. Confirma el comportamiento de las marcas de tiempo locales de Arrow anotadas con TIMESTAMP_MILLIS o TIMESTAMP_MICROS; el trabajo se considera completado cuando esta combinación se acepta sin descartar el nuevo tipo.

Escrito por el modelo de indexación a partir del texto del issue.

Evaluación

Stack tecnológico
java
Área
data-engineering
Tipo de issue
Error
Dificultad
4/5
Tiempo estimado
3-5 días
Estado de actividad
Estancado
Claridad
Bastante claro
Aptitud para principiantes
35/100

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