Aman Sinha has posted comments on this change. ( http://gerrit.cloudera.org:8080/18543 )
Change subject: IMPALA-11301: Fix extreme = and != selectivity for NDV=1 ...................................................................... Patch Set 2: Code-Review+2 (2 comments) http://gerrit.cloudera.org:8080/#/c/18543/1/fe/src/main/java/org/apache/impala/analysis/BinaryPredicate.java File fe/src/main/java/org/apache/impala/analysis/BinaryPredicate.java: http://gerrit.cloudera.org:8080/#/c/18543/1/fe/src/main/java/org/apache/impala/analysis/BinaryPredicate.java@267 PS1, Line 267: if (distinctValues == 1) distinctValues = 2; > Yes, and I do think that 0.5 is "more right" than 1. Yeah the NOT col = 1 is a good use case to justify this. I am good with it. In any case the cardinality will be rounded to the next integer value. http://gerrit.cloudera.org:8080/#/c/18543/1/fe/src/main/java/org/apache/impala/analysis/BinaryPredicate.java@273 PS1, Line 273: if (op_ == Operator.DISTINCT_FROM && rChildIsNull) { > I have changed the patch to only affect ndv=1. Thanks for making the change to do an explicit check. The presence or absence of a value is not possible to be handled through NDV alone. If we had Histogram or Most Common Values, those keep track of actual values which would help. Marking this resolved. -- To view, visit http://gerrit.cloudera.org:8080/18543 To unsubscribe, visit http://gerrit.cloudera.org:8080/settings Gerrit-Project: Impala-ASF Gerrit-Branch: master Gerrit-MessageType: comment Gerrit-Change-Id: I6b5334a8d7d6ca46a450ff98ae03e5269faaa3c6 Gerrit-Change-Number: 18543 Gerrit-PatchSet: 2 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]> Gerrit-Comment-Date: Wed, 18 May 2022 22:37:51 +0000 Gerrit-HasComments: Yes
