Comments on: SQL SERVER – Parallelism – Row per Processor – Row per Thread

By: SQLAuthority News – A Monthly Round Up of SQLAuthority Blog Posts Journey to SQL Authority with Pinal Dave

Sat, 31 Jul 2010 10:38:47 +0000

[...] SQL SERVER – Parallelism – Row per Processor – Row per Thread [...]

By: Feodor Georgiev

Feodor Georgiev — Fri, 16 Jul 2010 11:59:10 +0000

If you would like to know which queries are currently executing with parallelism, here you can find a query which will give you this information: http://feodorgeorgiev.com/blog/2010/07/find-queries-using-parallelism/. The query shreds the cached plans.

By: SQL SERVER – Parallelism – Row per Processor – Row per Thread – Thread 0 Journey to SQL Authority with Pinal Dave

Sun, 11 Jul 2010 01:32:01 +0000

[...] Read the answer over SQL SERVER – Parallelism – Row per Processor – Row per Thread. [...]

By: Mateus

Mateus — Fri, 09 Jul 2010 20:51:11 +0000

Thread 0 is the forked process and probably acts as a synchronizer / controller

By: SQL SERVER – View XML Query Plans in SSMS as Graphical Execution Plan Journey to SQL Authority with Pinal Dave

Sat, 03 Jul 2010 01:31:08 +0000

[...] 3, 2010 by pinaldave Earlier I wrote a blog post on SQL SERVER – Parallelism – Row per Processor – Row per Thread, where I mentioned the XML Plan. As a follow up on the blog post, I received the request to send [...]

By: Manoj Kumar

Manoj Kumar — Fri, 02 Jul 2010 05:31:26 +0000

Thread 0 is the coordinator thread which is not resposible to process any rows. It collects all the rows processed by other threads and show as query result.

Here thered 1 and 2 are not processing equal nuber of rows. i think ,thread 1 might have some other load processing on it.

Thanks
Manoj kumar

By: Feodor Georgiev

Feodor Georgiev — Fri, 02 Jul 2010 04:45:53 +0000

The thread 0 is shown in all operators of the execution plan and is called a synchronizing thread. The thread’s function is to gather all the stream from all parallel threads and bring the result to the client.

By: Marko Parkkola

Marko Parkkola — Fri, 02 Jul 2010 03:55:33 +0000

Thread 0 is used in synchronization of the other threads. It gather all the worker threads and their output data. It does not do actual data fetching so it has ActualRows always set to zero. A quote from MSDN blog:

“The reason is “MAXDOP is always specified per operator in the execution plan and not per execution plan”.

…

1 thread is used for parallel gather streams operator to collect and converge the parallel thread output from the Nested Loop join operator. This thread is basically a synchronizing thread (also referred as Thread 0 IN xml plan) which is used when there is parallelism in the execution plan of the query.”

http://blogs.msdn.com/b/sqlserverfaq/archive/2009/01/05/why-do-i-see-more-threads-per-spid-in-sysprocesses-than-maxdop.aspx