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From Kirk True <>
Subject Re: Batch update efficiency with composite key
Date Fri, 20 Jul 2012 22:04:48 GMT
I was aware of the read-then-write pattern for counters, but not 
secondary indexes. I'll have to take a look into that.


On 07/20/2012 02:32 AM, aaron morton wrote:
> I'm assuming the logical row is in a CQL 3 CF  with composite 
> It will still be a no look write. The exception being secondary 
> indexes and counters which include reads in the write path.
> Cheers
> -----------------
> Aaron Morton
> Freelance Developer
> @aaronmorton
> On 20/07/2012, at 10:26 AM, Kirk True wrote:
>> 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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