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https://issues.apache.org/jira/browse/OPTIQ-341?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Julian Hyde closed OPTIQ-341.
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> Redundant AggregateRel for IN subquery
> --------------------------------------
>
> Key: OPTIQ-341
> URL: https://issues.apache.org/jira/browse/OPTIQ-341
> Project: Optiq
> Issue Type: Bug
> Reporter: Aman Sinha
> Assignee: Julian Hyde
> Fix For: 0.9.1-incubating
>
>
> The following query against TPCH creates 2 AggregateRels for the IN
> subquery....one for the Group-By and one for the DISTINCT on the same column.
> Since Group-by is already doing the distinct, the second AggregateRel is
> redundant and hurts performance.
> {code:sql}
> SELECT n_name FROM nation
> WHERE n_regionkey IN (SELECT r_regionkey FROM region
> GROUP BY r_regionkey);
> ProjectRel(n_name=[$2])
> JoinRel(condition=[=($3, $4)], joinType=[inner])
> ProjectRel($f0=[$0], $f1=[$1], $f2=[$2], $f3=[$1])
> EnumerableTableAccessRel(table=[[dfs, TpchSf1, nation]])
> AggregateRel(group=[{0}])
> AggregateRel(group=[{0}])
> ProjectRel(r_regionkey=[$1])
> EnumerableTableAccessRel(table=[[dfs, TpchSf1, region]])
> {code}
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