GitHub user ueshin opened a pull request:
https://github.com/apache/spark/pull/19607
[SPARK-22395][SQL][PYTHON] Fix the behavior of timestamp values for Pandas
to respect session timezone
## What changes were proposed in this pull request?
When converting Pandas DataFrame/Series from/to Spark DataFrame using
`toPandas()` or pandas udfs, timestamp values behave to respect Python system
timezone instead of session timezone.
For example, let's say we use `"America/Los_Angeles"` as session timezone
and have a timestamp value `"1970-01-01 00:00:01"` in the timezone. Btw, I'm in
Japan so Python timezone would be `"Asia/Tokyo"`.
The timestamp value from current `toPandas()` will be the following:
```
>>> spark.conf.set("spark.sql.session.timeZone", "America/Los_Angeles")
>>> df = spark.createDataFrame([28801],
"long").selectExpr("timestamp(value) as ts")
>>> df.show()
+-------------------+
| ts|
+-------------------+
|1970-01-01 00:00:01|
+-------------------+
>>> df.toPandas()
ts
0 1970-01-01 17:00:01
```
As you can see, the value becomes `"1970-01-01 17:00:01"` because it
respects Python timezone.
As we discussed in #18664, we consider this behavior is a bug and the value
should be `"1970-01-01 00:00:01"`.
## How was this patch tested?
Added tests and existing tests.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/ueshin/apache-spark issues/SPARK-22395
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/19607.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #19607
----
commit 4735e5981ecf3a4bce50ce86f706e25830f4a801
Author: Takuya UESHIN <ues...@databricks.com>
Date: 2017-10-23T06:27:22Z
Add a conf to make Pandas DataFrame respect session local timezone.
commit 1f85150dc5b26df21dca6bad2ef4eaec342c4400
Author: Takuya UESHIN <ues...@databricks.com>
Date: 2017-10-23T08:09:16Z
Fix toPandas() behavior.
commit 5c08ecf247bfe7e14afcdef8eba1c25cb3b68634
Author: Takuya UESHIN <ues...@databricks.com>
Date: 2017-10-23T09:15:47Z
Modify pandas UDFs to respect session timezone.
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