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From Aaron Morton <>
Subject Re: Read before Write
Date Sun, 29 Aug 2010 02:51:32 GMT
If you are reading and making decisions about what to write just remember there are no transactions.
You are essentially running at a Read Uncommitted level of transaction isolation, with regard
of batch mutations (a mutation for a single row is atomic).

If you can it may be less headache to write without looking first.


On 28 Aug 2010, at 00:57, Daniel Doubleday <> wrote:

> Hi people
> I was wondering if anyone already benchmarked such a situation:
> I have:
> day of year (row key) -> SomeId (column key) -> byte[0]
> I need to make sure that I write SomeId, but in around 80% of the cases it will be already
present (so I would essentially replace it with itself). RF will be 2.
> So should I rather just write all the time (given that cassandra is so fast on write)
or should I read and write only if not present?
> Cheers,
> Daniel

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