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https://issues.apache.org/jira/browse/ARROW-14518?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17436611#comment-17436611
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Kenta Murata commented on ARROW-14518:
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Arrow's decimal number is completely different from {{BigDecimal}}. The former
is a fixed-point number whereas the latter is a floating-point number.
The best approach is introducing the new fixed-point number system for Arrow's
decimal numbers on the Ruby side.
The second-best approach for me is letting {{Arrow::Decimal128ArrayBuilder}}
support arbitrary precisions and scales. That can be done by pooling
{{BigDecimal}} values.
I's OK to add the new property in {{BigDecimal}} to obtain the number of digits
following the decimal dot for assisting the latter case. Maybe, the suitable
name of this property is {{BigDecimal#scale}}.
> [Ruby] ArrayBuilder doesn't work correctly with Decimal
> -------------------------------------------------------
>
> Key: ARROW-14518
> URL: https://issues.apache.org/jira/browse/ARROW-14518
> Project: Apache Arrow
> Issue Type: Bug
> Components: Ruby
> Reporter: Kanstantsin Ilchanka
> Priority: Minor
>
> When trying to convert raw data with decimal values to Arrow::Table error
> received
>
> {code:java}
> Arrow::Table.new(x: [BigDecimal('1.1')])
> ArgumentError: wrong arguments: Arrow::Decimal128ArrayBuilder#initialize():
> available signatures: (data_type:
> interface(Arrow::Decimal128DataType(GArrowDecimal128DataType)))
> {code}
> I guess this is because Decimal128ArrayBuilder expects Decimal128DataType in
> initialiser, however I'm not sure how to correctly and effectively detect
> precision and scale from array of BigDecimal
>
> {code:java}
> Arrow::VERSION
> => "5.0.0"{code}
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