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From Sylvain Lebresne <sylv...@datastax.com>
Subject Re: Batch update efficiency with composite key
Date Sat, 21 Jul 2012 10:11:23 GMT
On Sat, Jul 21, 2012 at 12:04 AM, Kirk True <kirk@mustardgrain.com> wrote:
> I was aware of the read-then-write pattern for counters, but not secondary
> indexes. I'll have to take a look into that.

Fyi, if you are interested by the subject,
https://issues.apache.org/jira/browse/CASSANDRA-2897 is relevant.

--
Sylvain


>
> Thanks.
>
>
> On 07/20/2012 02:32 AM, aaron morton wrote:
>
> I'm assuming the logical row is in a CQL 3 CF  with composite PRIMARYKEY
> http://www.datastax.com/dev/blog/whats-new-in-cql-3-0
>
> 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
> http://www.thelastpickle.com
>
> 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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