[GitHub] [druid] clintropolis commented on a change in pull request #9648: SQL: More straightforward handling of join planning.

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clintropolis commented on a change in pull request #9648: SQL: More straightforward handling of join planning.
URL: https://github.com/apache/druid/pull/9648#discussion_r406109085
 
 

 ##########
 File path: sql/src/main/java/org/apache/druid/sql/calcite/rel/CostEstimates.java
 ##########
 @@ -74,13 +74,19 @@
    * Multiplier to apply to an outer query via {@link DruidOuterQueryRel}. Encourages pushing down time-saving
    * operations to the lowest level of the query stack, because they'll have bigger impact there.
    */
-  static final double MULTIPLIER_OUTER_QUERY = 0.1;
+  static final double MULTIPLIER_OUTER_QUERY = .1;
 
   /**
-   * Multiplier to apply to a join when the left-hand side is a subquery. Encourages avoiding subqueries. Subqueries
-   * inside joins must be inlined, which incurs substantial reduction in scalability, so this high number is justified.
+   * Cost to add to a join when either side is a subquery. Strongly encourages avoiding subqueries, since they must be
+   * inlined and then the join must run on the Broker.
    */
-  static final double MULTIPLIER_JOIN_SUBQUERY = 1000000000;
+  static final double COST_JOIN_SUBQUERY = 1e5;
 
 Review comment:
   Out of curiosity where did these numbers come from? Experiments I guess?

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