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From David Strauss <da...@davidstrauss.net>
Subject Re: Manual Conflict Resolution in Cassandra
Date Tue, 26 Apr 2011 01:34:02 GMT
On Mon, 2011-04-25 at 03:50 -0700, Milind Parikh wrote:
> I suppose the term 'silently dropped' is a matter of perspective. C
> makes an explicit automated choice of latest-timestamp-wins. In
> certain situations, this is not the appropriate choice.

I would still insist that using Cassandra and expecting different
behavior makes the *usage* inappropriate, not Cassandra's design. You
*can* fairly say that Cassandra's design limits its potential uses, but
that's subtly different.

As an analogy:
If the engine in a Ford Focus can't tow a trailer with 20 tons of cargo,
you wouldn't say, "In certain situations, the engine Ford chose for the
Focus is not appropriate." No, the inappropriate thing would be choosing
a Focus to tow such a load. The trade-off of not being able to tow 20
tons was intentionally made to maximize fuel-efficiency, lower cost,
reduce complexity, or some other reasonable goal.

In Cassandra, the decision to resolve conflicts by keeping the item with
the later timestamp resulted from careful consideration of the options
(especially vector clocks). And, even if the current design is the
product of minimizing complexity, that is a valid design goal and not an
"inappropriate choice."

Cassandra may eventually gain the capability you're requesting, but
please stop pretending it's a bug or sign of bad judgment.

David

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