You are viewing a plain text version of this content. The canonical link for it is here.
Posted to issues-all@impala.apache.org by "Joe McDonnell (Jira)" <ji...@apache.org> on 2023/06/22 04:01:00 UTC
[jira] [Created] (IMPALA-12233) Partitioned hash join with a limit can hang when using mt_dop>0
Joe McDonnell created IMPALA-12233:
--------------------------------------
Summary: Partitioned hash join with a limit can hang when using mt_dop>0
Key: IMPALA-12233
URL: https://issues.apache.org/jira/browse/IMPALA-12233
Project: IMPALA
Issue Type: Bug
Components: Backend
Affects Versions: Impala 4.3.0
Reporter: Joe McDonnell
After encountering a hung query on an Impala cluster, we were able to reproduce it in the Impala developer environment with these steps:
{noformat}
use tpcds;
set mt_dop=2;
select ss_cdemo_sk from store_sales where ss_sold_date_sk = (select max(ss_sold_date_sk) from store_sales) group by ss_cdemo_sk limit 1;{noformat}
The problem reproduces with limit values up to 183, then at limit 184 and higher it doesn't reproduce.
Taking stack traces show a thread waiting for a cyclic barrier:
{noformat}
0 libpthread.so.0!__pthread_cond_wait + 0x216
1 impalad!impala::CyclicBarrier::Wait<impala::PhjBuilder::DoneProbingHashPartitions(const int64_t*, impala::BufferPool::ClientHandle*, impala::RuntimeProfile*, std::deque<std::unique_ptr<impala::PhjBuilderPartition> >*, impala::RowBatch*)::<lambda()> > [condition-variable.h : 49 + 0xc]
2 impalad!impala::PhjBuilder::DoneProbingHashPartitions(long const*, impala::BufferPool::ClientHandle*, impala::RuntimeProfile*, std::deque<std::unique_ptr<impala::PhjBuilderPartition, std::default_delete<impala::PhjBuilderPartition> >, std::allocator<std::unique_ptr<impala::PhjBuilderPartition, std::default_delete<impala::PhjBuilderPartition> > > >*, impala::RowBatch*) [partitioned-hash-join-builder.cc : 766 + 0x25]
3 impalad!impala::PartitionedHashJoinNode::DoneProbing(impala::RuntimeState*, impala::RowBatch*) [partitioned-hash-join-node.cc : 1189 + 0x28]
4 impalad!impala::PartitionedHashJoinNode::GetNext(impala::RuntimeState*, impala::RowBatch*, bool*) [partitioned-hash-join-node.cc : 599 + 0x15]
5 impalad!impala::StreamingAggregationNode::GetRowsStreaming(impala::RuntimeState*, impala::RowBatch*) [streaming-aggregation-node.cc : 115 + 0x14]
6 impalad!impala::StreamingAggregationNode::GetNext(impala::RuntimeState*, impala::RowBatch*, bool*) [streaming-aggregation-node.cc : 77 + 0x15]
7 impalad!impala::FragmentInstanceState::ExecInternal() [fragment-instance-state.cc : 446 + 0x15]
8 impalad!impala::FragmentInstanceState::Exec() [fragment-instance-state.cc : 104 + 0xf]
9 impalad!impala::QueryState::ExecFInstance(impala::FragmentInstanceState*) [query-state.cc : 956 + 0xf]{noformat}
Adding some debug logging around locations that go through that cyclic barrier, we see one Impalad where it is expecting two threads and only one arrives:
{noformat}
I0621 18:28:19.926551 210363 partitioned-hash-join-builder.cc:766] 2a4787b28425372d:ac6bd96200000004] DoneProbingHashPartitions: num_probe_threads_=2
I0621 18:28:19.927855 210362 streaming-aggregation-node.cc:136] 2a4787b28425372d:ac6bd96200000003] the number of rows (93) returned from the streaming aggregation node has exceeded the limit of 1
I0621 18:28:19.928887 210362 query-state.cc:958] 2a4787b28425372d:ac6bd96200000003] Instance completed. instance_id=2a4787b28425372d:ac6bd96200000003 #in-flight=4 status=OK{noformat}
Other instances that don't have a stuck thread see both threads arrive:
{noformat}
I0621 18:28:19.926223 210358 partitioned-hash-join-builder.cc:766] 2a4787b28425372d:ac6bd96200000005] DoneProbingHashPartitions: num_probe_threads_=2
I0621 18:28:19.926326 210359 partitioned-hash-join-builder.cc:766] 2a4787b28425372d:ac6bd96200000006] DoneProbingHashPartitions: num_probe_threads_=2{noformat}
So, there must be a codepath that skips going through the cyclic barrier.
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
---------------------------------------------------------------------
To unsubscribe, e-mail: issues-all-unsubscribe@impala.apache.org
For additional commands, e-mail: issues-all-help@impala.apache.org