[ https://issues.apache.org/jira/browse/SPARK-20939?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Takeshi Yamamuro updated SPARK-20939: ------------------------------------- Issue Type: Improvement (was: Bug) > Do not duplicate user-defined functions while optimizing logical query plans > ---------------------------------------------------------------------------- > > Key: SPARK-20939 > URL: https://issues.apache.org/jira/browse/SPARK-20939 > Project: Spark > Issue Type: Improvement > Components: Optimizer, SQL > Affects Versions: 2.1.0 > Reporter: Lovasoa > Priority: Minor > Labels: logical_plan, optimizer > > Currently, while optimizing a query plan, spark pushes filters down the query > plan tree, so that > {code:title=LogicalPlan} > Join Inner, (a = b) > +- Filter UDF(a) > +- Relation A > +- Relation B > {code} > becomes > {code:title=Optimized LogicalPlan} > Join Inner, (a = b) > +- Filter UDF(a) > +- Relation A > +- Filter UDF(b) > +- Relation B > {code} > In general, it is a good thing to push down filters as it reduces the number > of records that will go through the join. > However, in the case where the filter is an user-defined function (UDF), we > cannot know if the cost of executing the function twice will be higher than > the eventual cost of joining more elements or not. > So I think that the optimizer shouldn't move the user-defined function in the > query plan tree. The user will still be able to duplicate the function if he > wants to. > See this question on stackoverflow: > https://stackoverflow.com/questions/44291078/how-to-tune-the-query-planner-and-turn-off-an-optimization-in-spark -- This message was sent by Atlassian JIRA (v6.3.15#6346) --------------------------------------------------------------------- To unsubscribe, e-mail: issues-unsubscr...@spark.apache.org For additional commands, e-mail: issues-h...@spark.apache.org