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Posted to issues@hive.apache.org by "wangmeng (JIRA)" <ji...@apache.org> on 2015/06/09 10:54:00 UTC
[jira] [Updated] (HIVE-10971) count(*) with count(distinct) gives
wrong results when hive.groupby.skewindata=true
[ https://issues.apache.org/jira/browse/HIVE-10971?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
wangmeng updated HIVE-10971:
----------------------------
Description:
When hive.groupby.skewindata=true, the following query based on TPC-H gives wrong results:
{code}
set hive.groupby.skewindata=true;
select l_returnflag, count(*), count(distinct l_linestatus)
from lineitem
group by l_returnflag
limit 10;
{code}
The query plan shows that it generates only one MapReduce job instead of two theoretically, which is dictated by hive.groupby.skewindata=true.
The problem arises only when {noformat}count(*){noformat} and {noformat}count(distinct){noformat} exist together.
was:
When hive.groupby.skewindata=true, the following query based on TPC-H gives wrong results:
{code}
set hive.groupby.skewindata=true;
select l_returnflag, count(*), count(distinct l_linestatus)
from lineitem
group by l_returnflag
limit 10;
{code}
The query plan shows that it generates only one MapReduce job instead of two, which is dictated by hive.groupby.skewindata=true.
The problem arises only when {noformat}count(*){noformat} and {noformat}count(distinct){noformat} exist together.
> count(*) with count(distinct) gives wrong results when hive.groupby.skewindata=true
> -----------------------------------------------------------------------------------
>
> Key: HIVE-10971
> URL: https://issues.apache.org/jira/browse/HIVE-10971
> Project: Hive
> Issue Type: Bug
> Components: Hive
> Affects Versions: 1.2.0
> Reporter: wangmeng
> Assignee: wangmeng
>
> When hive.groupby.skewindata=true, the following query based on TPC-H gives wrong results:
> {code}
> set hive.groupby.skewindata=true;
> select l_returnflag, count(*), count(distinct l_linestatus)
> from lineitem
> group by l_returnflag
> limit 10;
> {code}
> The query plan shows that it generates only one MapReduce job instead of two theoretically, which is dictated by hive.groupby.skewindata=true.
> The problem arises only when {noformat}count(*){noformat} and {noformat}count(distinct){noformat} exist together.
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