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From Kirk True <k...@mustardgrain.com>
Subject Re: Batch update efficiency with composite key
Date Thu, 19 Jul 2012 22:26:34 GMT
In Cassandra you don't read-then-write updates, you just write the updates.

Sorry for being dense, but can you clarify a logical vs. physical row?

Batching is useful for reducing round trips to the server.

On 07/18/2012 06:18 AM, Leonid Ilyevsky wrote:
>
> I have a question about efficiency of updates to a CF with composite key.
>
> Let say I have 100 of logical rows to update, and they all belong to 
> the same physical wide row. In my naïve understanding (correct me if I 
> am wrong), in order to update a logical row, Cassandra has to retrieve 
> the whole physical row, add columns to it, and put it back. So I put 
> all my 100 updates in a batch and send it over. Would Cassandra be 
> smart enough to recognize that they all belong to one physical row, 
> retrieve it once, do all the updates and put it back once? Is my batch 
> thing even relevant in this case? What happens if I just send updates 
> one by one?
>
> I want to understand why I should use batches. I don't really care 
> about one timestamp for all records, I only care about efficiency. So 
> I thought, I want to at least save on the number of remote calls, but 
> I also wonder what happens on Cassandra side.
>
>
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