[jira] [Created] (CALCITE-3665) Better estimate join row count when one of the sides is known to be unique

["Vladimir Sitnikov (Jira)" <ji...@apache.org>]

Vladimir Sitnikov created CALCITE-3665:
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             Summary: Better estimate join row count when one of the sides is known to be unique
                 Key: CALCITE-3665
                 URL: https://issues.apache.org/jira/browse/CALCITE-3665
             Project: Calcite
          Issue Type: Bug
          Components: core
    Affects Versions: 1.21.0
            Reporter: Vladimir Sitnikov


For instance:
1) select from emp e left join  dept d on (e.X = d.id)
This query can't multiply rows, so its row count estimation is rowCount(join.left)

2) select from dept d right join emp e on (d.id = e.X)
This query can't multiply rows, so its row count estimation is rowCount(join.right)

3) select from emp e join  dept d on (e.id = d.id)
The rows can't be multiplied here as well

Currently, Calcite estimates the number of rows as left*right which is an overestimation in many cases :(



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