gianm commented on a change in pull request #9648: SQL: More straightforward
handling of join planning.
URL: https://github.com/apache/druid/pull/9648#discussion_r406462893
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File path:
sql/src/main/java/org/apache/druid/sql/calcite/rel/CostEstimates.java
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@@ -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:
Mostly I made them up, but then verified through experiments that they
achieve the plans that we want to achieve.
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