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From Michael Kjellman <mkjell...@barracuda.com>
Subject Re: Column Slice Query performance after deletions
Date Sat, 02 Mar 2013 18:42:42 GMT
What is your gc_grace set to? Sounds like as the number of tombstones records increase your
performance decreases. (Which I would expect)

On Mar 2, 2013, at 10:28 AM, "Víctor Hugo Oliveira Molinar" <vhmolinar@gmail.com<mailto:vhmolinar@gmail.com>>
wrote:

I have a daily maintenance of my cluster where I truncate this column family. Because its
data doesnt need to be kept more than a day.
Since all the regular operations on it finishes around 4 hours before finishing the day. I
regurlarly run a truncate on it followed by a repair at the end of the day.

And every day, when the operations are started(when are only few deleted columns), the performance
looks pretty well.
Unfortunately it is degraded along the day.


On Sat, Mar 2, 2013 at 2:54 PM, Michael Kjellman <mkjellman@barracuda.com<mailto:mkjellman@barracuda.com>>
wrote:
When is the last time you did a cleanup on the cf?

On Mar 2, 2013, at 9:48 AM, "Víctor Hugo Oliveira Molinar" <vhmolinar@gmail.com<mailto:vhmolinar@gmail.com>>
wrote:

> Hello guys.
> I'm investigating the reasons of performance degradation for my case scenario which follows:
>
> - I do have a column family which is filled of thousands of columns inside a unique row(varies
between 10k ~ 200k). And I do have also thousands of rows, not much more than 15k.
> - This rows are constantly updated. But the write-load is not that intensive. I estimate
it as 100w/sec in the column family.
> - Each column represents a message which is read and processed by another process. After
reading it, the column is marked for deletion in order to keep it out from the next query
on this row.
>
> Ok, so, I've been figured out that after many insertions plus deletion updates, my queries(
column slice query ) are taking more time to be performed. Even if there are only few columns,
lower than 100.
>
> So it looks like that the longer is the number of columns being deleted, the longer is
the time spent for a query.
> -> Internally at C*, does column slice query ranges among deleted columns?
> If so, how can I mitigate the impact in my queries? Or, how can I avoid those deleted
columns?

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