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https://issues.apache.org/jira/browse/HIVE-2693?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13534319#comment-13534319
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Mark Grover commented on HIVE-2693:
-----------------------------------
Thanks for your comments, [~hagleitn]. Yeah, the right thing moving forward
would be to update BinarySortableSerDe to support BigDecimal. When I thinking
of the best way to serialize BigDecimal, the sign and scale part were easy but
I wasn't able to come up with a space efficient way to store and arbitrary
number of digits so they are in-order byte sortable. Correct me if I am wrong
but seems like you are suggesting 1 byte per digit which would work (if the
lengths are equal) but can be dangerous since we are "exploding" an arbitrarily
long integer. Having said that, given Hive's historical philosophy of ignoring
malicious intent users, I am ok with moving forward with that approach.
On a related note, let's talk about the scale.
13267 has a scale of 0 and digits 13267
132.67 has a scale of 2 and digits 13267
132670 has a scale of -1 and digits 13267
So, it seems like the lower scale always means bigger number for positive
numbers, so shouldn't we do
{code}
<scale>: -scale for positive numbers (sign byte 1) and scale for negative
numbers (sign byte 0)
{code}
instead of
{code}
<scale>: scale integer if sign byte 1, -scale integer otherwise
{code}
which you suggested in your previous comment. I am basically asking to flip it
around since negative numbers have sign byte 0 and positive have sign byte.
BTW, feel free to contact me offline if you want to bounce around some ideas!
> Add DECIMAL data type
> ---------------------
>
> Key: HIVE-2693
> URL: https://issues.apache.org/jira/browse/HIVE-2693
> Project: Hive
> Issue Type: New Feature
> Components: Query Processor, Types
> Affects Versions: 0.10.0
> Reporter: Carl Steinbach
> Assignee: Prasad Mujumdar
> Attachments: 2693_7.patch, 2693_8.patch, 2693_fix_all_tests1.patch,
> HIVE-2693-10.patch, HIVE-2693-11.patch, HIVE-2693-1.patch.txt,
> HIVE-2693-all.patch, HIVE-2693-fix.patch, HIVE-2693.patch,
> HIVE-2693-take3.patch, HIVE-2693-take4.patch
>
>
> Add support for the DECIMAL data type. HIVE-2272 (TIMESTAMP) provides a nice
> template for how to do this.
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