[jira] [Updated] (ARROW-1749) [C++] Handle range of Decimal128 values that require 39 digits to be displayed

["Phillip Cloud (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ARROW-1749?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Phillip Cloud updated ARROW-1749:
---------------------------------
    Summary: [C++] Handle range of Decimal128 values that require 39 digits to be displayed  (was: [C++] Handle Min and Max Decimal128 values)

> [C++] Handle range of Decimal128 values that require 39 digits to be displayed
> ------------------------------------------------------------------------------
>
>                 Key: ARROW-1749
>                 URL: https://issues.apache.org/jira/browse/ARROW-1749
>             Project: Apache Arrow
>          Issue Type: Bug
>          Components: C++
>    Affects Versions: 0.7.1
>            Reporter: Phillip Cloud
>            Assignee: Phillip Cloud
>             Fix For: 0.8.0
>
>
> {{2 ** 127 - 1}} and {{-2 ** 127}} both require a 39th digit to be displayed as a decimal string.
> This means we do not have the ability to _display_ decimal values above {{10 ** 38 - 1}} even though we have the ability to _store_ them.
> For reference, Impala returns {{NULL}} when trying to cast {{2 ** 127 - 1}} to {{DECIMAL(38, 0)}}.
> A few next steps are in order:
> # Explicitly test this behavior
> # Avoid crashing or displaying garbage when we cannot display a number that can be stored
> # Make a decision about whether we want to eventually support range of values from {{10 ** 38}} to {{2 ** 127 - 1}} positive and {{-2 ** 127}} to {{-10 ** 38}} negative. This would require a larger integer type to hold the value just before being converted to a string.



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