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From "R. Verlangen" <ro...@us2.nl>
Subject Re: Row or Supercolumn with approximately n columns
Date Mon, 02 Jan 2012 21:38:00 GMT
@Aaron: Small side question, when do columns with a past TTL get removed?
On a repair, (minor) compaction, or .. ? Does it have a performance drop if
that's happening?

2012/1/2 aaron morton <aaron@thelastpickle.com>

> Even if you had compaction enforcing a limit on the number of columns in a
> row, there would still be issues with concurrent writes at the same time
> and with read-repair. i.e. node a says the this is the first n columns but
> node b says something else, you only know who is correct at read time.
>
> Have you considered using a TTL on the columns ?
>
> Depending on the use case you could also consider have writes periodically
> or randomly trim the data size, or trim on reads.
>
> It will also make sense to partition the time series data into different
> rows, and Viva la Standard Column Families!
>
> Hope that helps.
>
> -----------------
> Aaron Morton
> Freelance Developer
> @aaronmorton
> http://www.thelastpickle.com
>
> On 25/12/2011, at 7:48 PM, Praveen Baratam wrote:
>
> Hello Everybody,
>
> Happy Christmas.
>
> I know that this topic has come up quiet a few times on Dev and User lists
> but did not culminate into a solution.
>
> http://www.mail-archive.com/user@cassandra.apache.org/msg15367.html
>
> The above discussion on User list talks about AbstractCompactionStrategy
> but I could not find any relevant documentation as its a fairly new feature
> in Cassandra.
>
> Let me state this necessity and use-case again.
>
> I need a ColumnFamily (CF) wide or SuperColumn (SC) wide option to
> approximately limit the number of columns to "n". "n" can vary a lot and
> the intention is to throw away stale data and not to maintain any hard
> limit on the CF or SC. Its very useful for storing time-series data where
> stale data is not necessary. The goal is to achieve this with minimum
> overhead and since compaction happens all the time it would be clever to
> implement it as part of compaction.
>
> Thanks in advance.
>
> Praveen
>
>
>

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