Github user wzhfy commented on a diff in the pull request:
https://github.com/apache/spark/pull/17546#discussion_r110826959
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/CostBasedJoinReorder.scala
---
@@ -218,28 +220,48 @@ object JoinReorderDP extends PredicateHelper with
Logging {
}
/**
- * Builds a new JoinPlan when both conditions hold:
+ * Builds a new JoinPlan if the following conditions hold:
* - the sets of items contained in left and right sides do not overlap.
* - there exists at least one join condition involving references from
both sides.
+ * - if star-join filter is enabled, allow the following combinations:
+ * 1) (oneJoinPlan U otherJoinPlan) is a subset of star-join
+ * 2) star-join is a subset of (oneJoinPlan U otherJoinPlan)
+ * 3) (oneJoinPlan U otherJoinPlan) is a subset of non star-join
+ *
* @param oneJoinPlan One side JoinPlan for building a new JoinPlan.
* @param otherJoinPlan The other side JoinPlan for building a new join
node.
* @param conf SQLConf for statistics computation.
* @param conditions The overall set of join conditions.
* @param topOutput The output attributes of the final plan.
+ * @param filters Join graph info to be used as filters by the search
algorithm.
* @return Builds and returns a new JoinPlan if both conditions hold.
Otherwise, returns None.
*/
private def buildJoin(
oneJoinPlan: JoinPlan,
otherJoinPlan: JoinPlan,
conf: SQLConf,
conditions: Set[Expression],
- topOutput: AttributeSet): Option[JoinPlan] = {
+ topOutput: AttributeSet,
+ filters: Option[JoinGraphInfo]): Option[JoinPlan] = {
if (oneJoinPlan.itemIds.intersect(otherJoinPlan.itemIds).nonEmpty) {
// Should not join two overlapping item sets.
return None
}
+ if (conf.joinReorderDPStarFilter && filters.isDefined) {
+ // Apply star-join filter, which ensures that tables in a star
schema relationship
+ // are planned together. The star-filter will eliminate joins among
star and non-star
+ // tables until the star joins are built. The following combinations
are allowed:
+ // 1. (oneJoinPlan U otherJoinPlan) is a subset of star-join
+ // 2. star-join is a subset of (oneJoinPlan U otherJoinPlan)
+ // 3. (oneJoinPlan U otherJoinPlan) is a subset of non star-join
+ val isValidJoinCombination =
+ JoinReorderDPFilters(conf).starJoinFilter(oneJoinPlan.itemIds,
otherJoinPlan.itemIds,
--- End diff --
This will create a new `JoinReorderDPFilters` instance every time we try to
build a join node.
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