[IMPALA-1622] Impala incorrectly handles double numbers with more than 19 significant decimal digits

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: Impala 2.0
• Fix Version/s: Impala 2.2
• Labels: ramp-up
• Assignee: Skye Wanderman-Milne
• Reporter: Simone
• Created: 18/Dec/14 11:34
• Updated: 04/Jan/17 23:58
• Resolved: 03/Feb/15 22:19

Description

I have created the following table:

create external table dev.impala_precision_test(
c1 String,
c2 Double
)
row format delimited fields terminated by '|'
location '/user/battaglias/impala_precision_test';

on a text file with these 2 rows of data:

a|1.12345678912345678912
b|1.1234567891234567891

The first number has 20 significant decimal digits, the second one 19.

This is the result retrieved by Impala (impala-shell), where the first number is incorrectly represented:

select *
from dev.impala_precision_test

c1	c2
a	0.9389893483863613
b	1.123456789123457

This is instead the result from Hive (Beeline shell), where both numbers are correctly rounded-off:

impala_double_bug.c1	impala_double_bug.c2
a	1.1234567891234568
b	1.1234567891234568

Also float data type, in Impala, seem suffer from the same problem.