[jira] [Commented] (ARROW-13439) [C++] Unify BasicDecimal128 and BasicDecimal256 classes

["Yibo Cai (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ARROW-13439?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17387856#comment-17387856 ] 

Yibo Cai commented on ARROW-13439:
----------------------------------

Looks it doesn't deserve the effort.
One possible approach is to derive BasicDecimal128 and 256 from a templated base class. It does reduces many common code. But the problem is I have to put all implementation code in header file, which is too big.
{code:cpp}
template <int BitWidth>
class BasicDecimal {
  ......
  std::array<uint64_t, BidWidth/64> array_;
}

class BasicDecimal128 : public BasicDecimal<128> {
  ......
};

class BasicDecimal256 : public BasicDecimal<128> {
  ......
};
{code}

> [C++] Unify BasicDecimal128 and BasicDecimal256 classes
> -------------------------------------------------------
>
>                 Key: ARROW-13439
>                 URL: https://issues.apache.org/jira/browse/ARROW-13439
>             Project: Apache Arrow
>          Issue Type: Improvement
>          Components: C++
>            Reporter: Yibo Cai
>            Assignee: Yibo Cai
>            Priority: Major
>             Fix For: 6.0.0
>
>
> BasicDecimal128 uses two dedicated int64 (higher, lower) to store the value. It's possible to use std::array<uint64, 2> to store the value, just like BasicDecimal256 does, and to unify the two classes.
> As decimal operations are quite expensive, guess this indirection won't cause performance loss.



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