Spark timestamp difference

问题

I am trying to do a timestamp difference in Spark and it is not working as expected.

Below is how I'm trying to

import org.apache.spark.sql.functions.*
df = df.withColumn("TimeStampDiff", from_unixtime(unix_timestamp(df.col("TimeStampHigh"), "HH:mm:ss").minus(unix_timestamp(df.col("TimeStampLow"), "HH:mm:ss")),"HH:mm:ss"))

Values

TimeStampHigh - 15:57:01
TimeStampLow - 00:11:57

It returns me a result of 10:45:04 Expected output - 15:45:04

My other alternative is to go to an UDF with Java implementation.

Any pointers will help.

回答1:

That's because from_unixtime (emphasis mine):

Converts the number of seconds from unix epoch (1970-01-01 00:00:00 UTC) to a string representing the timestamp of that moment in the current system time zone in the given format.

Clearly your system or JVM is not configured to use UTC time.

You should do one of the following:

Configure JVM to use appropriate time zone (-Duser.timezone=UTC for both spark.executor.extraJavaOptions and spark.driver.extraJavaOptions).
Set spark.sql.session.timeZone to use appropriate time zone.

Example:

scala> val df = Seq(("15:57:01", "00:11:57")).toDF("TimeStampHigh", "TimeStampLow")
df: org.apache.spark.sql.DataFrame = [TimeStampHigh: string, TimeStampLow: string]

scala> spark.conf.set("spark.sql.session.timeZone", "GMT-5")  // Equivalent to your current settings

scala> df.withColumn("TimeStampDiff", from_unixtime(unix_timestamp(df.col("TimeStampHigh"), "HH:mm:ss").minus(unix_timestamp(df.col("TimeStampLow"), "HH:mm:ss")),"HH:mm:ss")).show
+-------------+------------+-------------+
|TimeStampHigh|TimeStampLow|TimeStampDiff|
+-------------+------------+-------------+
|     15:57:01|    00:11:57|     10:45:04|
+-------------+------------+-------------+


scala> spark.conf.set("spark.sql.session.timeZone", "UTC")  // With UTC

scala> df.withColumn("TimeStampDiff", from_unixtime(unix_timestamp(df.col("TimeStampHigh"), "HH:mm:ss").minus(unix_timestamp(df.col("TimeStampLow"), "HH:mm:ss")),"HH:mm:ss")).show
+-------------+------------+-------------+
|TimeStampHigh|TimeStampLow|TimeStampDiff|
+-------------+------------+-------------+
|     15:57:01|    00:11:57|     15:45:04|
+-------------+------------+-------------+

来源：https://stackoverflow.com/questions/49878598/spark-timestamp-difference

标签

java

apache-spark

timestamp