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https://issues.apache.org/jira/browse/SPARK-45786?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Dongjoon Hyun closed SPARK-45786.
---------------------------------
> Inaccurate Decimal multiplication and division results
> ------------------------------------------------------
>
> Key: SPARK-45786
> URL: https://issues.apache.org/jira/browse/SPARK-45786
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 3.2.4, 3.3.3, 3.4.1, 3.5.0, 4.0.0
> Reporter: Kazuyuki Tanimura
> Assignee: Kazuyuki Tanimura
> Priority: Blocker
> Labels: correctness, pull-request-available
> Fix For: 3.4.2, 3.5.1, 4.0.0
>
>
> Decimal multiplication and division results may be inaccurate due to rounding
> issues.
> h2. Multiplication:
> {code:scala}
> scala> sql("select -14120025096157587712113961295153.858047 *
> -0.4652").show(truncate=false)
> +----------------------------------------------------+
>
> |(-14120025096157587712113961295153.858047 * -0.4652)|
> +----------------------------------------------------+
> |6568635674732509803675414794505.574764 |
> +----------------------------------------------------+
> {code}
> The correct answer is
> {quote}6568635674732509803675414794505.574763
> {quote}
> Please note that the last digit is 3 instead of 4 as
>
> {code:scala}
> scala>
> java.math.BigDecimal("-14120025096157587712113961295153.858047").multiply(java.math.BigDecimal("-0.4652"))
> val res21: java.math.BigDecimal = 6568635674732509803675414794505.5747634644
> {code}
> Since the factional part .574763 is followed by 4644, it should not be
> rounded up.
> h2. Division:
> {code:scala}
> scala> sql("select -0.172787979 /
> 533704665545018957788294905796.5").show(truncate=false)
> +-------------------------------------------------+
> |(-0.172787979 / 533704665545018957788294905796.5)|
> +-------------------------------------------------+
> |-3.237521E-31 |
> +-------------------------------------------------+
> {code}
> The correct answer is
> {quote}-3.237520E-31
> {quote}
> Please note that the last digit is 0 instead of 1 as
>
> {code:scala}
> scala>
> java.math.BigDecimal("-0.172787979").divide(java.math.BigDecimal("533704665545018957788294905796.5"),
> 100, java.math.RoundingMode.DOWN)
> val res22: java.math.BigDecimal =
> -3.237520489418037889998826491401059986665344697406144511563561222578738E-31
> {code}
> Since the factional part .237520 is followed by 4894..., it should not be
> rounded up.
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