Hello Aman Sinha, Gabor Kaszab, Abhishek Rawat, Zoltan Borok-Nagy, Impala
Public Jenkins,
I'd like you to reexamine a change. Please visit
http://gerrit.cloudera.org:8080/18543
to look at the new patch set (#4).
Change subject: IMPALA-11301: Fix extreme != selectivity for NDV=1
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IMPALA-11301: Fix extreme != selectivity for NDV=1
The original selectivity of 1.0 - 1.0/ndv makes sense for
large NDVs, but the result is 0.0 in case of ndv==1, which
leads to a cardinality of 1 even for huge tables. The new
selectivity is 0.5.
Note that as the formula for = is not changed (1.0/ndv),
NOT col="const" will still lead to 0.0 selectivity if ndv=1.
Changing the formula of NOT or = would have caused a lot of
subtle changes in plans in tests, so I don't want to touch
those before coming to wider agreement about the correct
approach.
IMPALA-7601 contains some discussion about these formulas.
Testing:
- added a regression test
Change-Id: I6b5334a8d7d6ca46a450ff98ae03e5269faaa3c6
---
M fe/src/main/java/org/apache/impala/analysis/BinaryPredicate.java
M fe/src/test/java/org/apache/impala/planner/CardinalityTest.java
2 files changed, 12 insertions(+), 1 deletion(-)
git pull ssh://gerrit.cloudera.org:29418/Impala-ASF refs/changes/43/18543/4
--
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Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-MessageType: newpatchset
Gerrit-Change-Id: I6b5334a8d7d6ca46a450ff98ae03e5269faaa3c6
Gerrit-Change-Number: 18543
Gerrit-PatchSet: 4
Gerrit-Owner: Csaba Ringhofer <[email protected]>
Gerrit-Reviewer: Abhishek Rawat <[email protected]>
Gerrit-Reviewer: Aman Sinha <[email protected]>
Gerrit-Reviewer: Csaba Ringhofer <[email protected]>
Gerrit-Reviewer: Gabor Kaszab <[email protected]>
Gerrit-Reviewer: Impala Public Jenkins <[email protected]>
Gerrit-Reviewer: Zoltan Borok-Nagy <[email protected]>
