alamb commented on code in PR #9800:
URL: https://github.com/apache/arrow-datafusion/pull/9800#discussion_r1541124956
##########
datafusion/physical-plan/src/joins/utils.rs:
##########
@@ -968,6 +991,78 @@ fn estimate_inner_join_cardinality(
}
}
+/// Estimates semi join cardinality based on statistics.
+///
+/// The estimation result is either zero, in cases inputs statistics are
non-overlapping
+/// or equal to number of rows for outer input.
+fn estimate_semi_join_cardinality(
Review Comment:
Long term it would be really nice to pull these types of calculations into
some trait (aka an extensibility API)
##########
datafusion/physical-plan/src/joins/utils.rs:
##########
@@ -888,10 +888,45 @@ fn estimate_join_cardinality(
})
}
- JoinType::LeftSemi
- | JoinType::RightSemi
- | JoinType::LeftAnti
- | JoinType::RightAnti => None,
+ JoinType::LeftSemi | JoinType::LeftAnti => {
+ let cardinality = estimate_semi_join_cardinality(
Review Comment:
it doesn't seem correct to me that the same calculation is used for both
Semi and Anti joins (shouldn't they be the inverse of each other?)
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