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Posted to issues@calcite.apache.org by "Quan Chao (Jira)" <ji...@apache.org> on 2021/09/28 06:48:00 UTC

[jira] [Created] (CALCITE-4809) Mixed merge join result is incomplete

Quan Chao created CALCITE-4809:
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             Summary: Mixed merge join result is incomplete 
                 Key: CALCITE-4809
                 URL: https://issues.apache.org/jira/browse/CALCITE-4809
             Project: Calcite
          Issue Type: Bug
          Components: linq4j
    Affects Versions: 1.26.0
            Reporter: Quan Chao


The result of mixed merge join is incomplete. The merge join relies on the row data of the two tables to be sorted by the join field, but if the left table itself is a left join, nulls may appear due to mismatches, causing the entire join to end early。

  EG：

   t1 left join t2 on t1.id=t2.id join t3 on t2.id=t3.id;

   t1 rows: 1,2,3,4

   t2 rows: 1,2,4

   t3 rows: 1.2.3.4

   final result is:1,2, 4 is lost;

   when MergeJoinEnumerator left (t1xt2) come to: 3,null, right (t3) is 3, the null <3 cause left  advance finish wrong



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