We did a wholesale revamp of decimal behaviour going from CDH5 to CDH6. The default behaviour all changed in CDH6.0: https://docs.cloudera.com/documentation/enterprise/6/release-notes/topics/rg_cdh_600_new_features.html#decimal_v2   There's a whole epic JIRA capturing the changes: https://issues.apache.org/jira/browse/IMPALA-4072 . I think https://issues.apache.org/jira/browse/IMPALA-4370 might be the specific fix that you're seeing, based on your analysis. The fix version for that change is Impala 2.9.0, so the code change is in CDH5.15.2, but it was done behind the DECIMAL_V2 query option, which wasn't a supported option until CDH6.   IN CDH6 you can toggle the behaviour with the DECIMAL_V2 query option (it will eventually be removed, but was kept for backward compatibility). ... View more