[
https://issues.apache.org/jira/browse/HIVE-17844?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16213072#comment-16213072
]
Zoltan Ivanfi commented on HIVE-17844:
--------------------------------------
[~akolb], yes, that's true, but it doesn't represent the initial user-supplied
number faithfully any more.
If the user supplies the value 125.32, it can not be represented as a float
precisely, but rounding rules during displaying that float will still display
125.32. However, when converting that float to double, different, more precise
rounding rules start to apply, resulting in 125.31999969482422 getting
displayed instead of 125.32. It is true that the double value is precisely the
same as the float value, yet although none of them is precisely the same as the
user-supplied value, the float gets displayed as the original value and the
double isn't.
If 125.32 is stored directly to a double, then it is approximated more
precisely and will display correctly. When it is stored as a float and then
converted to a double, this is no longer true.
> Hive JDBC driver converts floats to doubles, changing values slightly
> ---------------------------------------------------------------------
>
> Key: HIVE-17844
> URL: https://issues.apache.org/jira/browse/HIVE-17844
> Project: Hive
> Issue Type: Bug
> Components: JDBC
> Reporter: Zoltan Ivanfi
>
> When querying data through Hive's JDBC driver, float values are automatically
> converted to doubles and will slightly differ from values seen when directly
> querying the data using a textual SQL interface.
> Please note that by slight difference I don't only mean additional zeroes at
> the end, but an actual numeric difference in the displayed value. This is the
> result of the different precision used when displaying double values, as
> discussed
> [here|https://stackoverflow.com/questions/17504833/why-converting-from-float-to-double-changes-the-value],
> for example.
--
This message was sent by Atlassian JIRA
(v6.4.14#64029)
