[
https://issues.apache.org/jira/browse/DRILL-4119?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15025071#comment-15025071
]
Zelaine Fong commented on DRILL-4119:
-------------------------------------
Per discussion at today's Drill hangout, Jacques mentioned that one of the
differences resulting from the port is dealing with Java not supporting
unsigneds.
> Skew in hash distribution for varchar (and possibly other) types of data
> ------------------------------------------------------------------------
>
> Key: DRILL-4119
> URL: https://issues.apache.org/jira/browse/DRILL-4119
> Project: Apache Drill
> Issue Type: Bug
> Components: Functions - Drill
> Affects Versions: 1.3.0
> Reporter: Aman Sinha
> Assignee: Aman Sinha
> Fix For: 1.4.0
>
>
> We are seeing substantial skew for an Id column that contains varchar data of
> length 32. It is easily reproducible by a group-by query:
> {noformat}
> Explain plan for SELECT SomeId From table GROUP BY SomeId;
> ...
> 01-02 HashAgg(group=[{0}])
> 01-03 Project(SomeId=[$0])
> 01-04 HashToRandomExchange(dist0=[[$0]])
> 02-01 UnorderedMuxExchange
> 03-01 Project(SomeId=[$0],
> E_X_P_R_H_A_S_H_F_I_E_L_D=[castInt(hash64AsDouble($0))])
> 03-02 HashAgg(group=[{0}])
> 03-03 Project(SomeId=[$0])
> {noformat}
> The string id happens to be of the following type:
> {noformat}
> e4b4388e8865819126cb0e4dcaa7261d
> {noformat}
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
