Marcel Kornacker has posted comments on this change. Change subject: IMPALA-2805: Order conjuncts based on selectivity and cost ......................................................................
Patch Set 13: (1 comment) http://gerrit.cloudera.org:8080/#/c/2598/13/fe/src/main/java/com/cloudera/impala/planner/PlanNode.java File fe/src/main/java/com/cloudera/impala/planner/PlanNode.java: Line 657: double backoff_exp = 1.0 / (double) (sortedConjuncts.size() + 1); > I follow the intuition, but I think we'd need a more complex algorithm to t the backoff affects the additive term (totalcost - e.cost), which is scaled by selectivity ^ backoff - it will decrease the impact of the selectivity of e, and that selectivity is different for each e. in other words, it will affect the cost calculation for each e differently. i don't see how it would be immaterial to the ordering. that would only be the case if it added or subtracted a constant amount for each e. -- To view, visit http://gerrit.cloudera.org:8080/2598 To unsubscribe, visit http://gerrit.cloudera.org:8080/settings Gerrit-MessageType: comment Gerrit-Change-Id: I02279a26fbc6308ac5eb819d78345fc010469034 Gerrit-PatchSet: 13 Gerrit-Project: Impala Gerrit-Branch: cdh5-trunk Gerrit-Owner: Thomas Tauber-Marshall <[email protected]> Gerrit-Reviewer: Alex Behm <[email protected]> Gerrit-Reviewer: Henry Robinson <[email protected]> Gerrit-Reviewer: Marcel Kornacker <[email protected]> Gerrit-Reviewer: Matthew Jacobs <[email protected]> Gerrit-Reviewer: Mostafa Mokhtar <[email protected]> Gerrit-Reviewer: Thomas Tauber-Marshall <[email protected]> Gerrit-HasComments: Yes
