SQL Server Performance Forum – Threads Archive
Regarding Broadcast Parallelism.
Hi, I have written a Query that shows a stream of Broadcast Exchange operator Parallelism. I can’t understand the basic reason behind it as I know mainly three types of Exchange Operators, viz Distribute, Gather and Repartition. Can anybody highlight regarding this type of Parallelism as I am not able to find any clue regarding it even in BOL. Regards, Arindam GangulyHave you set max degree of parallelism?
Are there any changes to the environment recently? Satya SKJ
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Hi Satya, I have checked the maximum degree of parallelism set to 0 ? Should I change it. If it is then to what value ? Pls advise. Regards,
Arindam Ganguly
My guess about Broadcast operators is that they send copies of all the data from a single stream out to multiple streams which kicks off the parallel operations. I have seen this in a hash join where the broadcast feeds into the building of a parallelised hash table. I guess it’s a newish exchange operator (hence not in BOL) that increases the number of alternative query plans to optimize between. I have only seen it used when the amount of data being broadcast was quite small. Regards
Stephen
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