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Description:
This wait type appears to be when a thread for certain batch-mode query operations is waiting for other such threads to finish initializing.
(Books Online description: N/A)
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Added in SQL Server version:
2012
Removed in SQL Server version:
N/A
Extended Events wait_type value:
The map_key value in sys.dm_xe_map_values is 696 in 2012 and 714 in 2014 RTM. After 2014 RTM, you must check the DMV to get the latest value as some map_key values have changed in later builds.
Other information:
I have not seen this thread be a noticeable contention point.
Known occurrences in SQL Server (list number matches call stack list):
- Waiting for other parallel threads to finish initializing while running a hash join involving a columnstore index
And many other similar callstacks.
Abbreviated call stacks (list number matches known occurrences list):
- SOS_Task::PostWait+0x6f
WaitableBase::Wait+0xb7
CBpQScanColumnStoreScan::InitRowsetColumnBatch+0x808
CBpQScanColumnStoreScan::BpOpen+0x5a
CBpQScan::DefaultOpen+0x48
CBpQScanHashJoin::Main+0xf7
CBpQScanHashJoin::BpGetNextBatch+0x28
CQScanBatchHelper::GetRow+0x7c
CQScanXProducerNew::GetRowHelper+0x63
CQScanXProducerNew::GetRow+0x15
FnProducerOpen+0x5b
FnProducerThread+0x80b
SubprocEntrypoint+0x1201
SOS_Task::Param::Execute+0x231
SOS_Scheduler::RunTask+0xad