where not in ( query block)
condition will been change to LeftSemi join in optimizer rule RewritePredicateSubquery.
Then as cloud-fan said, it will be change to a BroadCastNestLoopJoin
On 10/23/2019 20:55，Wenchen Fan<cloud0...@gmail.com> wrote：
I haven't looked into your query yet, just want to let you know that: Spark can only pick BroadcastNestedLoopJoin to implement left/right join. If the table is very big, then OOM happens.Maybe there is an algorithm to implement left/right join in a distributed environment without broadcast, but currently Spark is only able to deal with it using broadcast.On Wed, Oct 23, 2019 at 6:02 PM zhangliyun <kelly...@126.com> wrote:Hi all:i want to ask a question about broadcast nestloop join? from google i know, thatleft outer/semi join and right outer/semi join will use broadcast nestloop.and in some cases, when the input data is very small, it is suitable to use. so herehow to define the input data very small? what parameter decides the threshold? I just want to disable it ( i found that set spark.sql.autoBroadcastJoinThreshold= -1 is no work for sql:select a.key1 from testdata1 as a where a.key1 not in (select key3 from testdata3) )```explain cost select a.key1 from testdata1 as a where a.key1 not in (select key3 from testdata3);== Physical Plan ==*(1) Project [key1#90]+- BroadcastNestedLoopJoin BuildRight, LeftAnti, ((key1#90 = key3#92) || isnull((key1#90 = key3#92))):- HiveTableScan [key1#90], HiveTableRelation `default`.`testdata1`, org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe, [key1#90, value1#91]+- BroadcastExchange IdentityBroadcastMode+- HiveTableScan [key3#92], HiveTableRelation `default`.`testdata3`, org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe, [key3#92, value3#93]```my question is1. why in not in subquery , BroadcastNestedLoopJoin is still used even i set spark.sql.autoBroadcastJoinThreshold= -12. which spark parameter decides enable/disable BroadcastNestedLoopJoin.Appreciate if you have suggestionBest RegardsKelly Zhang
