swuferhong commented on code in PR #21530:
URL: https://github.com/apache/flink/pull/21530#discussion_r1065269586
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flink-table/flink-table-planner/src/main/scala/org/apache/flink/table/planner/plan/rules/logical/RewriteMultiJoinConditionRule.scala:
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@@ -45,7 +48,12 @@ class RewriteMultiJoinConditionRule
// currently only supports all join types are INNER join
val isAllInnerJoin = multiJoin.getJoinTypes.forall(_ eq JoinRelType.INNER)
val (equiJoinFilters, _) = partitionJoinFilters(multiJoin)
- !multiJoin.isFullOuterJoin && isAllInnerJoin && equiJoinFilters.size > 1
+ val numJoinInputs = multiJoin.getInputs.size()
+ val dpThreshold = ShortcutUtils
+ .unwrapContext(multiJoin)
+ .getTableConfig
+ .get(OptimizerConfigOptions.TABLE_OPTIMIZER_BUSHY_JOIN_REORDER_THRESHOLD)
+ (numJoinInputs > dpThreshold) && !multiJoin.isFullOuterJoin &&
isAllInnerJoin && equiJoinFilters.size > 1
Review Comment:
For bushy join reorder, this is no need to rewrite multi join condition
while it will increase the search base of the bushy join reorder algorithm, but
it will not bring more possible join pairs for bushy join. Like `A J B J C`, `A
and B` have join condition, `B and C` have join condition.
`RewriteMultiJoinConditionRule` will add a new condition `A and C`: this is
useful for Lopt join rule, but for bushy join rule, the condition `A and B`
and `B and C` can get all three-tables join reorder result( `(A J B) J C` and
`(A J C) J B` and `(A J B) J C` ). Btw, I will add comment for why will do it.
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