Tim Armstrong has posted comments on this change. ( http://gerrit.cloudera.org:8080/16349 )
Change subject: IMPALA-7310: Partial fix for NDV cardinality with NULLs. ...................................................................... Patch Set 3: (1 comment) I think this makes sense to me - the only question really would be whether this should be broader and increase the NDV in all cases where we know there are nulls. I think fixing this really bad case first is OK though. http://gerrit.cloudera.org:8080/#/c/16349/3/fe/src/main/java/org/apache/impala/analysis/SlotRef.java File fe/src/main/java/org/apache/impala/analysis/SlotRef.java: http://gerrit.cloudera.org:8080/#/c/16349/3/fe/src/main/java/org/apache/impala/analysis/SlotRef.java@97 PS3, Line 97: && desc_.getStats().hasNullsStats() It might be safer to assume that there are nulls in the absence of null stats. Although I guess that is only relevant if we *do* have NDV and don't have null stats, which should be rare. -- To view, visit http://gerrit.cloudera.org:8080/16349 To unsubscribe, visit http://gerrit.cloudera.org:8080/settings Gerrit-Project: Impala-ASF Gerrit-Branch: master Gerrit-MessageType: comment Gerrit-Change-Id: Iec967053b4991f8c67cde62adf003cbd3f429032 Gerrit-Change-Number: 16349 Gerrit-PatchSet: 3 Gerrit-Owner: Shant Hovsepian <[email protected]> Gerrit-Reviewer: Aman Sinha <[email protected]> Gerrit-Reviewer: David Rorke <[email protected]> Gerrit-Reviewer: Impala Public Jenkins <[email protected]> Gerrit-Reviewer: Qifan Chen <[email protected]> Gerrit-Reviewer: Shant Hovsepian <[email protected]> Gerrit-Reviewer: Tim Armstrong <[email protected]> Gerrit-Comment-Date: Mon, 24 Aug 2020 16:59:14 +0000 Gerrit-HasComments: Yes
