[jira] [Created] (IMPALA-15526) tpcds-unmodified q78 joins cs_item_sk to itself instead of ss_item_sk

["Zoltán Borók-Nagy (Jira)" <ji...@apache.org>]

Zoltán Borók-Nagy created IMPALA-15526:
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             Summary: 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


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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