[SPARK-12297] Add work-around for Parquet/Hive int96 timestamp bug. - ASF JIRA

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Details

Type: Task
Status: Resolved
Priority: Major
Resolution: Fixed
Affects Version/s: None
Fix Version/s: 2.3.0
Component/s: Spark Core
Labels:
None

Description

Spark copied Hive's behavior for parquet, but this was inconsistent with other file formats, and inconsistent with Impala (which is the original source of putting a timestamp as an int96 in parquet, I believe). This made timestamps in parquet act more like timestamps with timezones, while in other file formats, timestamps have no time zone, they are a "floating time".

The easiest way to see this issue is to write out a table with timestamps in multiple different formats from one timezone, then try to read them back in another timezone. Eg., here I write out a few timestamps to parquet and textfile hive tables, and also just as a json file, all in the "America/Los_Angeles" timezone:

import org.apache.spark.sql.Row
import org.apache.spark.sql.types._

val tblPrefix = args(0)
val schema = new StructType().add("ts", TimestampType)
val rows = sc.parallelize(Seq(
  "2015-12-31 23:50:59.123",
  "2015-12-31 22:49:59.123",
  "2016-01-01 00:39:59.123",
  "2016-01-01 01:29:59.123"
).map { x => Row(java.sql.Timestamp.valueOf(x)) })
val rawData = spark.createDataFrame(rows, schema).toDF()

rawData.show()

Seq("parquet", "textfile").foreach { format =>
  val tblName = s"${tblPrefix}_$format"
  spark.sql(s"DROP TABLE IF EXISTS $tblName")
  spark.sql(
    raw"""CREATE TABLE $tblName (
          |  ts timestamp
          | )
          | STORED AS $format
     """.stripMargin)
  rawData.write.insertInto(tblName)
}

rawData.write.json(s"${tblPrefix}_json")

Then I start a spark-shell in "America/New_York" timezone, and read the data back from each table:

scala> spark.sql("select * from la_parquet").collect().foreach{println}
[2016-01-01 02:50:59.123]
[2016-01-01 01:49:59.123]
[2016-01-01 03:39:59.123]
[2016-01-01 04:29:59.123]

scala> spark.sql("select * from la_textfile").collect().foreach{println}
[2015-12-31 23:50:59.123]
[2015-12-31 22:49:59.123]
[2016-01-01 00:39:59.123]
[2016-01-01 01:29:59.123]

scala> spark.read.json("la_json").collect().foreach{println}
[2015-12-31 23:50:59.123]
[2015-12-31 22:49:59.123]
[2016-01-01 00:39:59.123]
[2016-01-01 01:29:59.123]

scala> spark.read.json("la_json").join(spark.sql("select * from la_textfile"), "ts").show()
+--------------------+
|                  ts|
+--------------------+
|2015-12-31 23:50:...|
|2015-12-31 22:49:...|
|2016-01-01 00:39:...|
|2016-01-01 01:29:...|
+--------------------+

scala> spark.read.json("la_json").join(spark.sql("select * from la_parquet"), "ts").show()
+---+
| ts|
+---+
+---+

The textfile and json based data shows the same times, and can be joined against each other, while the times from the parquet data have changed (and obviously joins fail).

This is a big problem for any organization that may try to read the same data (say in S3) with clusters in multiple timezones. It can also be a nasty surprise as an organization tries to migrate file formats. Finally, its a source of incompatibility between Hive, Impala, and Spark.

~~HIVE-12767~~ aims to fix this by introducing a table property which indicates the "storage timezone" for the table. Spark should add the same to ensure consistency between file formats, and with Hive & Impala.