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https://issues.apache.org/jira/browse/HIVE-13019?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15147807#comment-15147807
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Ruslan Dautkhanov commented on HIVE-13019:
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Thank you Gopal. Oracle has "RELY NOVALIDATE" option for constraints.. would it
be easier for Hive to start with something like that for PK/FK constraints? So
CBO has more information for optimizations. It does not have to actually check
if that constraint is relationship is actually true; it can just "rely" on that
constraint.. Is this already plan for Hive 2.0? Thanks again.
> Optimizer COLLECT_LIST/COLLECT_SET
> -----------------------------------
>
> Key: HIVE-13019
> URL: https://issues.apache.org/jira/browse/HIVE-13019
> Project: Hive
> Issue Type: Improvement
> Components: CBO, Logical Optimizer
> Reporter: Dustin Cote
> Priority: Minor
>
> Currently when using a COLLECT_SET/COLLECT_LIST that involves data from a
> single table, the aggregation is done after any JOIN operation that is
> present in the query. For example:
> {code}
> insert into table nested_customers_orders
> select c.*, collect_list(named_struct("oid", o.oid, "order_date": o.date...))
> from customers c inner join orders o on (c.cid = o.oid)
> group by o.oid, o.date,...
> {code}
> If we can tell the optimizer to perform the COLLECT_LIST first (where
> possible) we can see some performance gains in this pattern of query.
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