Jason Dere created HIVE-17103:
---------------------------------
Summary: HIVE-14251 severely impacts backward compatibility of
UNION ALL queries
Key: HIVE-17103
URL: https://issues.apache.org/jira/browse/HIVE-17103
Project: Hive
Issue Type: Bug
Components: Types
Affects Versions: 2.2.0
Reporter: Jason Dere
HIVE-14251 looks like it changed behavior of type conversion during UNION ALL
queries, where types that are of different primitive groups (date, string,
numeric, binary, boolean) cannot be unioned together with implicit conversions,
and requires an explicit type cast to the desired type.
That HIVE-14251 breaks backward compatibility is spelled out in the release
notes. However I'm wondering if this was the right fix - this has quite a big
impact on the usability of UNION ALL.
Some alternative suggestions:
1. Should we have simply not fixed HIVE-14251? While almost all DBMSs recommend
users to use explicit casts, a lot of people just rely on implicit casting (if
supported), and then do explicit casting if they want something other than the
default behavior. This might have been one of the times the user would want to
use explicit casts to override the default Hive behavior.
2. Try to specifically fix the case for HIVE-14251 (union behavior of date,
numeric). I was actually surprised union of date and numeric values worked,
because when I originally did DATE type I tried to make sure DATE was not
convertible to anything except string/timestamp. For example I don't think you
can actually explicitly cast DATE to INT. We could try to make this particular
implicit union conversion invalid (as well as any others we feel may not ).
cc [~aihuaxu] [~mohitsabharwal] [~ctang.ma] [~ashutoshc] [~aravindgopal]
[~sershe] as these are the names I've seen on HIVE-14251, as well as related
Jira HIVE-16050
--
This message was sent by Atlassian JIRA
(v6.4.14#64029)
