Paul Rogers has posted comments on this change. ( http://gerrit.cloudera.org:8080/11565 )
Change subject: IMPALA-7659: Simplify expression to collect NULLs count ...................................................................... Patch Set 5: (2 comments) A few comments. http://gerrit.cloudera.org:8080/#/c/11565/5//COMMIT_MSG Commit Message: http://gerrit.cloudera.org:8080/#/c/11565/5//COMMIT_MSG@10 PS5, Line 10: IMPALA-7655. This fix would be helpful for IMPALA-7310: if NDV=0, we need to know if nullCount > 0 to know if we should adjust NDV upward by one. (The planner includes nulls in NDV, statistics don't.) http://gerrit.cloudera.org:8080/#/c/11565/5/fe/src/main/java/org/apache/impala/analysis/ComputeStatsStmt.java File fe/src/main/java/org/apache/impala/analysis/ComputeStatsStmt.java: http://gerrit.cloudera.org:8080/#/c/11565/5/fe/src/main/java/org/apache/impala/analysis/ComputeStatsStmt.java@251 PS5, Line 251: " IS NULL THEN 1 ELSE NULL END)"); If this expression is faster than an if() function (IMPALA-7655), then does it makes sense to optimize the if() function in the planner so it benefits all queries rather than just changing this one? -- To view, visit http://gerrit.cloudera.org:8080/11565 To unsubscribe, visit http://gerrit.cloudera.org:8080/settings Gerrit-Project: Impala-ASF Gerrit-Branch: master Gerrit-MessageType: comment Gerrit-Change-Id: Ic68f8b4c3756eb1980ce299a602a7d56db1e507a Gerrit-Change-Number: 11565 Gerrit-PatchSet: 5 Gerrit-Owner: Anonymous Coward <piotr.findei...@gmail.com> Gerrit-Reviewer: Anonymous Coward <piotr.findei...@gmail.com> Gerrit-Reviewer: Bharath Vissapragada <bhara...@cloudera.com> Gerrit-Reviewer: Impala Public Jenkins <impala-public-jenk...@cloudera.com> Gerrit-Reviewer: Paul Rogers <par0...@yahoo.com> Gerrit-Reviewer: Tim Armstrong <tarmstr...@cloudera.com> Gerrit-Reviewer: Vuk Ercegovac <vercego...@cloudera.com> Gerrit-Comment-Date: Thu, 18 Oct 2018 22:25:52 +0000 Gerrit-HasComments: Yes
