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https://issues.apache.org/jira/browse/SPARK-22036?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16169074#comment-16169074
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Marco Gaido commented on SPARK-22036:
-------------------------------------
Maybe the "bad" part is that by default spark creates the columns as
{{Decimal(38, 18)}}. This is the problem. With a multiplication this leads to a
{{Decimal(38, 36)}}, which as you can easily understand is the root of the
problem of your operation. If you cast the two columns before the
multiplication, like {{ds("a").cast(DecimalType(20,14))}}, you won't have any
problem anymore.
Currently you should suggest Spark which are the right values to use.
> 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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