[SPARK-41554] fix changing of Decimal scale when scale decreased by m… #39099
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Can one of the admins verify this patch? |
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Hi @cloud-fan, @MaxGekk, @gengliangwang, would you be able to review? Thank you! |
cloud-fan
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Dec 27, 2022
sql/catalyst/src/test/scala/org/apache/spark/sql/types/DecimalSuite.scala
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| @@ -374,7 +374,7 @@ final class Decimal extends Ordered[Decimal] with Serializable { | |||
| if (scale < _scale) { | |||
| // Easier case: we just need to divide our scale down | |||
| val diff = _scale - scale | |||
| val pow10diff = POW_10(diff) | |||
| val pow10diff = POW_10(math.min(diff, MAX_LONG_DIGITS)) | |||
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Can we still use compact long to store the decimal value? Shall we go to the branch // Give up on using Longs; switch to BigDecimal, which we'll modify below?
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Compact long can still be used when diff > MAX_LONG_DIGITS. In this case longVal becomes 0, 1 or -1 depending on rounding, so using BigDecimal is not actually needed.
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Dec 28, 2022
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thanks, merging to master! |
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@fe2s can you create backport PRs for other branches? Thanks! |
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@cloud-fan thank you, which branches should fix also? 3.1, 3.2 and 3.3? |
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3.2 and 3.3, as they are both active branches. |
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…ore than 18 This is a backport PR for apache#39099 Closes apache#39381 from fe2s/branch-3.2-fix-decimal-scaling. Authored-by: oleksii.diagiliev <oleksii.diagiliev@workday.com> Signed-off-by: Sean Owen <srowen@gmail.com>
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…ore than 18
What changes were proposed in this pull request?
Fix
Decimalscaling that is stored as compact long internally when scale decreased by more than 18. For example,produces an exception
Another way to reproduce it with SQL query
The bug exists for Decimal that is stored using compact long only, it works fine with Decimal that uses
scala.math.BigDecimalinternally.Why are the changes needed?
Not able to execute the SQL query mentioned above. Please note, for my use case the SQL query is generated programatically, so I cannot optimize it manually.
Does this PR introduce any user-facing change?
Yes, it will allow scale Decimal properly that is not currently possible due to the exception.
How was this patch tested?
Tests were added. The fix affects the scale decrease only, but I decided to also include tests for scale increase as I didn't find them.