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From Sylvain Lebresne <sylv...@yakaz.com>
Subject Re: Caching is a full row?
Date Wed, 14 Apr 2010 07:02:33 GMT
Yes, it will put the whole row in cache even if you read only a bunch
of columns.
It means in particular that with row cache, every time you read a row,
the full row
will be read on a cache miss. Thus it may hurts you read badly in some scenario
(typically with big rows) instead of helping them. Enable row cache wisely :)

--
Sylvain

On Wed, Apr 14, 2010 at 3:06 AM, Paul Prescod <prescod@gmail.com> wrote:
> On Tue, Apr 13, 2010 at 5:26 PM, Rob Coli <rcoli@digg.com> wrote:
>> On 4/13/10 5:04 PM, Paul Prescod wrote:
>>>
>>> Am I correct in my understanding that the unit of caching (and
>>> fetching from disk?) is a full row?
>>
>> Cassandra has both a Key and a Row cache. Unfortunately there appears to be
>> no current wiki doc describing them. If you are looking into the topic, wiki
>> updates are always appreciated. :)
>
> Yeah, sorry I knew that but I was asking specifically about if there
> was any caching within a row that is more granular than the whole row.
> It looks to me like it doesn't just cache the columns you asked for,
> but all columns in the row. This obviously has some interesting
> implications for keys that are large "indexes" in a single row.
>
>  Paul Prescod
>

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