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From "Hiller, Dean" <>
Subject Re: Multi threads updating single row
Date Thu, 03 Jan 2013 19:34:41 GMT
My bad, I meant exactly that, there could be performance issues if you have multiple nodes
hitting the same row since that row work items are serialised.


From: aaron morton <<>>
Reply-To: "<>" <<>>
Date: Thursday, January 3, 2013 12:28 PM
To: "<>" <<>>
Subject: Re: Multi threads updating single row

Multiple nodes could be a problem
Not sure what you mean here Dean.

There are no issues with multiple clients, from multiple threads, processes or nodes inserting
/ updating to the same row.

There are potential performance issues though due to row level isolation used in the write
path. The first (internal) writing thread "wins" when updating a row, so any concurrent (internal)
write threads updating the same row must (again internally) restart their processing.

You will probably only see issues when you have 10's of clients continually updating the same
row. And then the size of  issue depends somewhat on the size of the inserts you are running.
i.e. a smaller insert size means less re-work.

There are also potential performance issues if you have secondary indexes on the row.

Hope that helps.

Aaron Morton
Freelance Cassandra Developer
New Zealand


On 4/01/2013, at 2:32 AM, "Hiller, Dean" <<>>

Multiple nodes could be a problem but multiple threads is probably just fine.  If you have
two threads write to the same column, the last one wins though so I hope your timestamps are
unique even across threads so you don't lose data ;).


From: Jay Svc <<><>>
Reply-To: "<><>"
Date: Wednesday, January 2, 2013 4:55 PM
To: "<><>"
Subject: Multi threads updating single row

Happy New Year Everyone..!

In the situation, there are multiple client thread updating or adding new columns in a same
row. These new columns is a time series data.

My Question is - Would multiple threads able to add columns to the same row? Do you see any
performance issues since there is a comparator and has to sort columns as they get added.
Do you see any loss of data or conflict due to mulitple thread updating data? I am expecting
high volumn of data coming on each one of those threads.

Thanks in advance.


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