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https://issues.apache.org/jira/browse/HIVE-3976?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13764646#comment-13764646
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Xuefu Zhang commented on HIVE-3976:
-----------------------------------
Thanks for sharing the thoughts. I think both 1) and 2) are regarding to
backward compatibility. If decimal is reserved for fixed precision/scale, then
there is no way to be fully backward compatible. That's because decimal, as
it's in hive, is fixed precision and variable scale. No matter what the new
default is for scale, there will be compatibility issue. To make things worse,
user doesn't even know the scale of the existing data.
As mentioned, if the adoption is low, it might make better sense for us to take
the pain and do it right. This is the stand point that the document takes.
Validity of the assumption is subject to discussion, of course.
As to non-generic UDFs, I think we need to educate user to avoid them unless
the whatever the default is exactly what he/she needs, which is unlikely in my
opinion: if they needs decimal(5, 2), decimal(6,3) will not make them happier.
> Support specifying scale and precision with Hive decimal type
> -------------------------------------------------------------
>
> Key: HIVE-3976
> URL: https://issues.apache.org/jira/browse/HIVE-3976
> Project: Hive
> Issue Type: Improvement
> Components: Query Processor, Types
> Reporter: Mark Grover
> Assignee: Xuefu Zhang
> Attachments: remove_prec_scale.diff
>
>
> HIVE-2693 introduced support for Decimal datatype in Hive. However, the
> current implementation has unlimited precision and provides no way to specify
> precision and scale when creating the table.
> For example, MySQL allows users to specify scale and precision of the decimal
> datatype when creating the table:
> {code}
> CREATE TABLE numbers (a DECIMAL(20,2));
> {code}
> Hive should support something similar too.
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