incubator-cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Russell Haering <russellhaer...@gmail.com>
Subject Re: quick question about data layout on disk
Date Sat, 11 Aug 2012 18:23:35 GMT
Your update doesn't go directly to an sstable (which are immutable),
it is first merged to an in-memory table. Eventually the memtable is
flushed to a new sstable.

See http://wiki.apache.org/cassandra/MemtableSSTable

On Sat, Aug 11, 2012 at 11:03 AM, Aaron Turner <synfinatic@gmail.com> wrote:
> So how does that work?  An sstable is for a single CF, but it can and
> likely will have multiple rows.  There is no read to write and as I
> understand it, writes are append operations.
>
> So if you have an sstable with say 26 different rows (A-Z) already in
> it with a bunch of columns and you add a new column to row J, how does
> Cassandra store the column/value pair on disk in a way to refer to row
> J without re-writing the row key or some representation of it?
>
> Thanks,
> Aaron
>
> On Fri, Aug 10, 2012 at 7:53 PM, Terje Marthinussen
> <tmarthinussen@gmail.com> wrote:
>> Rowkey is stored only once in any sstable file.
>>
>> That is, in the spesial case where you get sstable file per column/value, you are
correct, but normally, I guess most of us are storing more per key.
>>
>> Regards,
>> Terje
>>
>> On 11 Aug 2012, at 10:34, Aaron Turner <synfinatic@gmail.com> wrote:
>>
>>> Curious, but does cassandra store the rowkey along with every
>>> column/value pair on disk (pre-compaction) like Hbase does?  If so
>>> (which makes the most sense), I assume that's something that is
>>> optimized during compaction?
>>>
>>>
>>> --
>>> Aaron Turner
>>> http://synfin.net/         Twitter: @synfinatic
>>> http://tcpreplay.synfin.net/ - Pcap editing and replay tools for Unix & Windows
>>> Those who would give up essential Liberty, to purchase a little temporary
>>> Safety, deserve neither Liberty nor Safety.
>>>    -- Benjamin Franklin
>>> "carpe diem quam minimum credula postero"
>
>
>
> --
> Aaron Turner
> http://synfin.net/         Twitter: @synfinatic
> http://tcpreplay.synfin.net/ - Pcap editing and replay tools for Unix & Windows
> Those who would give up essential Liberty, to purchase a little temporary
> Safety, deserve neither Liberty nor Safety.
>     -- Benjamin Franklin
> "carpe diem quam minimum credula postero"

Mime
View raw message