e9145d41f3
### What changes were proposed in this pull request?
It fixes microseconds rebasing from the hybrid calendar (Julian + Gregorian) to Proleptic Gregorian calendar in the function `RebaseDateTime`.`rebaseJulianToGregorianMicros(zoneId: ZoneId, micros: Long): Long` in the case of local timestamp overlapping.
In the case of overlapping, we look ahead of 1 day to determinate which instant we should take - earlier or later zoned timestamp. If our current standard zone and DST offsets are equal to zone offset of the next date, we choose the later timestamp otherwise the earlier one. For example, the local timestamp **1945-11-18 01:30:00.0** can be mapped to two instants (microseconds since 1970-01-01 00:00:00Z): -761211000000000 or -761207400000000. If the first one is passed to `rebaseJulianToGregorianMicros()`, we take the earlier instant in Proleptic Gregorian calendar while rebasing **1945-11-18T01:30+09:00[Asia/Hong_Kong]** otherwise the later one **1945-11-18T01:30+08:00[Asia/Hong_Kong]**.
Note: The fix assumes that only one transition of standard or DST offsets can occur during a day.
### Why are the changes needed?
Current implementation of `rebaseJulianToGregorianMicros()` handles timestamps overlapping only during daylight saving time but overlapping can happen also during transition from one standard time zone to another one. For example in the case of `Asia/Hong_Kong`, the time zone switched from `Japan Standard Time` (UTC+9) to `Hong Kong Time` (UTC+8) on _Sunday, 18 November, 1945 01:59:59 AM_. The changes allow to handle the special case as well.
### Does this PR introduce _any_ user-facing change?
There is no behaviour change for timestamps of CE after 0001-01-01. The PR might affects timestamps of BCE for which the modified `rebaseJulianToGregorianMicros()` is called directly.
### How was this patch tested?
1. By existing tests in `DateTimeUtilsSuite`, `RebaseDateTimeSuite`, `DateFunctionsSuite`, `DateExpressionsSuite` and `TimestampFormatterSuite`.
2. Added new checks to `RebaseDateTimeSuite`.`SPARK-31959: JST -> HKT at Asia/Hong_Kong in 1945`:
```scala
assert(rebaseJulianToGregorianMicros(hkZid, rebasedEarlierMicros) === earlierMicros)
assert(rebaseJulianToGregorianMicros(hkZid, rebasedLaterMicros) === laterMicros)
```
3. Regenerated `julian-gregorian-rebase-micros.json` with the step of 30 minutes, and got the same JSON file. The JSON file isn't affected because previously it was generated with the step of 1 week. And the spike in diffs/switch points during 1 hour of timestamp overlapping wasn't detected.
Closes #28816 from MaxGekk/fix-overlap-julian-2-grep.
Authored-by: Max Gekk <max.gekk@gmail.com>
Signed-off-by: Wenchen Fan <wenchen@databricks.com>
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Apache Spark
Spark is a unified analytics engine for large-scale data processing. It provides high-level APIs in Scala, Java, Python, and R, and an optimized engine that supports general computation graphs for data analysis. It also supports a rich set of higher-level tools including Spark SQL for SQL and DataFrames, MLlib for machine learning, GraphX for graph processing, and Structured Streaming for stream processing.
Online Documentation
You can find the latest Spark documentation, including a programming guide, on the project web page. This README file only contains basic setup instructions.
Building Spark
Spark is built using Apache Maven. To build Spark and its example programs, run:
./build/mvn -DskipTests clean package
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More detailed documentation is available from the project site, at "Building Spark".
For general development tips, including info on developing Spark using an IDE, see "Useful Developer Tools".
Interactive Scala Shell
The easiest way to start using Spark is through the Scala shell:
./bin/spark-shell
Try the following command, which should return 1,000,000,000:
scala> spark.range(1000 * 1000 * 1000).count()
Interactive Python Shell
Alternatively, if you prefer Python, you can use the Python shell:
./bin/pyspark
And run the following command, which should also return 1,000,000,000:
>>> spark.range(1000 * 1000 * 1000).count()
Example Programs
Spark also comes with several sample programs in the examples directory.
To run one of them, use ./bin/run-example <class> [params]. For example:
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MASTER=spark://host:7077 ./bin/run-example SparkPi
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Please see the guidance on how to run tests for a module, or individual tests.
There is also a Kubernetes integration test, see resource-managers/kubernetes/integration-tests/README.md
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