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https://issues.apache.org/jira/browse/IMPALA-15526?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Michael Smith resolved IMPALA-15526.
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Fix Version/s: Impala 5.0.0
Resolution: Fixed
> tpcds-unmodified q78 joins cs_item_sk to itself instead of ss_item_sk
> ---------------------------------------------------------------------
>
> Key: IMPALA-15526
> URL: https://issues.apache.org/jira/browse/IMPALA-15526
> Project: IMPALA
> Issue Type: Bug
> Components: Infrastructure, Test
> Reporter: Zoltán Borók-Nagy
> Assignee: Zoltán Borók-Nagy
> Priority: Major
> Labels: performance
> Fix For: Impala 5.0.0
>
>
> testdata/workloads/tpcds-unmodified/queries/tpcds-q78.test:49 (master
> 1f34ea915e) has:
> {code:sql}
> left join cs on (cs_sold_year=ss_sold_year and cs_item_sk=cs_item_sk and
> cs_customer_sk=ss_customer_sk)
> {code}
> The TPC-DS specification, and the tpcds and tpcds_partitioned copies of the
> query, use cs_item_sk=ss_item_sk.
> With the typo, the cs join matches on (year, customer) only, so it becomes
> many-to-many, and the planner gives the self-equality the default 0.1
> selectivity. Results differ from the specification query, and performance
> numbers from this workload are not comparable with other engines or published
> TPC-DS results. Since tpcds-unmodified is the workload used for performance
> tests, the fix also changes baseline numbers.
> Fix: replace cs_item_sk=cs_item_sk with cs_item_sk=ss_item_sk.
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