[HIVE-3715] float and double calculation is inaccurate in Hive

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 0.10.0
• Component/s: SQL
• Assignee: Johnny Zhang
• Reporter: Johnny Zhang
• Created: 16/Nov/12 19:19
• Updated: 03/Sep/15 07:51

Description

I found this during debug the e2e test failures. I found Hive miss calculate the float and double value. Take float calculation as an example:

hive> select f from all100k limit 1;
48308.98
hive> select f/10 from all100k limit 1;
4830.898046875 <--added 04875 in the end
hive> select f*1.01 from all100k limit 1;
48792.0702734375 <--should be 48792.0698

It might be essentially the same problem as http://effbot.org/pyfaq/why-are-floating-point-calculations-so-inaccurate.htm. But since e2e test compare the results with mysql and seems mysql does it right, so it is worthy fixing it in Hive.

Issue Links

• is related to: HIVE-2586 Float comparison doesn't work