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: (2 comments) 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; Would it make sense to instead treat the NDV as 1 in this case? Since if the NDV estimate is lower, we expect the join cardinality to be higher. I.e. Math.max(lhsAdjNdv, rhsAdjNdv) becomes Math.max(1, Math.max(lhsAdjNdv, rhsAdjNdv)) http://gerrit.cloudera.org:8080/#/c/11901/1/fe/src/test/java/org/apache/impala/planner/PlannerTest.java File fe/src/test/java/org/apache/impala/planner/PlannerTest.java: http://gerrit.cloudera.org:8080/#/c/11901/1/fe/src/test/java/org/apache/impala/planner/PlannerTest.java@713 PS1, Line 713: checkCardinality(query, 0, 1); } newline -- 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: Impala Public Jenkins <[email protected]> Gerrit-Reviewer: Tim Armstrong <[email protected]> Gerrit-Comment-Date: Wed, 07 Nov 2018 20:28:03 +0000 Gerrit-HasComments: Yes
