Thanks for the reply. I saw IMPALA-3902 <https://issues.apache.org/jira/browse/IMPALA-3902> seems to add support for multithread execution. It describes the goal is to support running multiple fragment instances on a single node, is that means coordinator generate multiple instances for a plan fragment on a single node so that starts multiple exchange nodes to receive data and process? Or it starts instances for different plan fragments for preparing the streaming?
2017-10-25 22:08 GMT+08:00 Jeszy <jes...@gmail.com>: > Hello JJ, > > No, currently Impala uses one thread to execute the join (without > regard for the amount of partitions that fit into memory). > > HTH > > On 25 October 2017 at 05:44, 俊杰陈 <cjjnj...@gmail.com> wrote: > > Hi > > > > When Impala does a partitioned join on a node, it split the build input > > into partitions until a partition can fit into memory and consume the > probe > > input then do the join and output rows. > > > > My question is will impala schedule multiple tasks to do join if multiple > > partitions fit into memory, or iterate over partitions? And for one > > partition does it use multiple threads to do join? Thanks in advanced. > > > > > > JJ > -- Thanks & Best Regards
