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https://issues.apache.org/jira/browse/SPARK-22036?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16169129#comment-16169129
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Olivier Blanvillain edited comment on SPARK-22036 at 9/16/17 11:24 PM:
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Adding a cast indeed prevents getting null values. However this solution is
less than satisfactory as the resulting multiplications are _less_ precise on
{{BigDecimal}} than on {{Double}}.
Here is an example. We compute the product of two numbers:
{{0.0000199735164642333984375}} and {{-0.000010430812835693359375}}. Below are
the result of this multiplication by the JVM as {{java.lang.Double}} (double),
by Spark using {{.cast(DecimalType(20,14))}} (casted), and finally using
unlimited precision arithmetic (actual):
{{double: -2.083400119090584E-10}}
{{casted: -2.083400119509193464E-10}}
{{actual: -2.083400119090583757497370243072509765625E-10}}
was (Author: olivierblanvillain):
Adding a cast indeeds prevents getting null values. However this solution is
less than satisfactory as the resulting mutliplications are _less_ precise on
{{BigDecimal}} than on {{Double}}.
Here is an example. We compute the product of two numbers:
{{0.0000199735164642333984375}} and {{-0.000010430812835693359375}}. Below are
the result of this multiplication by the JVM as {{java.lang.Double}} (double),
by Spark using {{.cast(DecimalType(20,14))}} (casted), and finally using
unlimited precision arithmetic (actual):
{{double: -2.083400119090584E-10}}
{{casted: -2.083400119509193464E-10}}
{{actual: -2.083400119090583757497370243072509765625E-10}}
> BigDecimal multiplication sometimes returns null
> ------------------------------------------------
>
> Key: SPARK-22036
> URL: https://issues.apache.org/jira/browse/SPARK-22036
> Project: Spark
> Issue Type: Bug
> Components: Spark Core
> Affects Versions: 2.2.0
> Reporter: Olivier Blanvillain
>
> The multiplication of two BigDecimal numbers sometimes returns null. This
> issue we discovered while doing property based testing for the frameless
> project. Here is a minimal reproduction:
> {code:java}
> object Main extends App {
> import org.apache.spark.{SparkConf, SparkContext}
> import org.apache.spark.sql.SparkSession
> import spark.implicits._
> val conf = new
> SparkConf().setMaster("local[*]").setAppName("REPL").set("spark.ui.enabled",
> "false")
> val spark =
> SparkSession.builder().config(conf).appName("REPL").getOrCreate()
> implicit val sqlContext = spark.sqlContext
> case class X2(a: BigDecimal, b: BigDecimal)
> val ds = sqlContext.createDataset(List(X2(BigDecimal(-0.1267333984375),
> BigDecimal(-1000.1))))
> val result = ds.select(ds("a") * ds("b")).collect.head
> println(result) // [null]
> }
> {code}
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