[
https://issues.apache.org/jira/browse/HIVE-790?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12748277#action_12748277
]
Zheng Shao commented on HIVE-790:
---------------------------------
Overall it looks good.
Can you measure the performance impact by running a union of 2 simple "select
*"? If it's less than 5%, let's just leave it as it is. Otherwise let's open
another JIRA to improve it.
UnionOperator's close() also needs to be synchronized.
bq. We need both both states since if we just have 1 state (CLOSE) and assign
it in the beginning, if there are two parents to the operator, when the first
parent call close(), this operator will set it state to CLOSE and just return
without calling close() to all its children (since the other parent has not
been closed). When the second parent call close(), it just return since its
state is already closed. So this end up all children are not closed. We should
not remove the CLOSE state checkup in the beginning since that may cause an
operator being closed multiple times.
Can we do this:
{code}
public void close(boolean abort) {
// only close when all parents are closed.
if (!allParentsAreClosed()) {
return;
}
this.state = CLOSE;
for (int i=0; i<children.size(); i++) {
children.get(i).close(abort);
}
}
{code}
> race condition related to ScriptOperator + UnionOperator
> --------------------------------------------------------
>
> Key: HIVE-790
> URL: https://issues.apache.org/jira/browse/HIVE-790
> Project: Hadoop Hive
> Issue Type: Bug
> Reporter: Zheng Shao
> Assignee: Ning Zhang
> Attachments: Hive-790.patch, Hive-790_2.patch
>
>
> ScriptOperator uses a second thread to output the rows to the children
> operators. In a corner case which contains a union, 2 threads might be
> outputting data into the same operator hierarchy and caused race conditions.
> {code}
> CREATE TABLE tablea (cola STRING);
> SELECT *
> FROM (
> SELECT TRANSFORM(cola)
> USING 'cat'
> AS cola
> FROM tablea
> UNION ALL
> SELECT cola as cola
> FROM tablea
> ) a;
> {code}
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
