Tim Armstrong has posted comments on this change. ( http://gerrit.cloudera.org:8080/11901 )
Change subject: IMPALA-7528: Fix division by zero when computing cardinalities ...................................................................... Patch Set 1: (1 comment) http://gerrit.cloudera.org:8080/#/c/11901/1/fe/src/main/java/org/apache/impala/planner/JoinNode.java File fe/src/main/java/org/apache/impala/planner/JoinNode.java: http://gerrit.cloudera.org:8080/#/c/11901/1/fe/src/main/java/org/apache/impala/planner/JoinNode.java@368 PS1, Line 368: if (lhsAdjNdv <= 0 && rhsAdjNdv <= 0) return 0; > Tim qq, the actual cardinality (result) would still be 0 right? What is the We don't know for sure it's zero. I think mostly NDV == 0 occurs if there are all nulls (but I'm not totally sure if there are other cases), and definitely plain inner joins return zero rows if either side is all nulls. But other join conditions and modes handled by this function return > 0 rows if both sides are null (e.g. outer joins, <=> operator, etc). -- To view, visit http://gerrit.cloudera.org:8080/11901 To unsubscribe, visit http://gerrit.cloudera.org:8080/settings Gerrit-Project: Impala-ASF Gerrit-Branch: master Gerrit-MessageType: comment Gerrit-Change-Id: Ieedd51d3ad6131a4ea2a5883f05104e6a0f2cd14 Gerrit-Change-Number: 11901 Gerrit-PatchSet: 1 Gerrit-Owner: Bikramjeet Vig <[email protected]> Gerrit-Reviewer: Bharath Vissapragada <[email protected]> Gerrit-Reviewer: Bikramjeet Vig <[email protected]> Gerrit-Reviewer: Impala Public Jenkins <[email protected]> Gerrit-Reviewer: Tim Armstrong <[email protected]> Gerrit-Comment-Date: Wed, 07 Nov 2018 23:36:03 +0000 Gerrit-HasComments: Yes
