how many rows can one partion key hold?

[wateray <wa...@163.com>]

Hi all,
My team is using Cassandra as our database. We have one question as below.
As we know, the row with the some partition key will be stored in the some node.
But how many rows can one partition key hold? What is it depend on? The node's volume or partition data size or partition rows size(the number of rows)?
 When one partition's data is  extreme large, the write/read will slow?
Can anyone show me some exist usecases.
 thanks!


 

Re: how many rows can one partion key hold?

[Jason Wee <pe...@gmail.com>]

you might want to read here
http://wiki.apache.org/cassandra/CassandraLimitations

jason

On Fri, Feb 27, 2015 at 2:44 PM, wateray <wa...@163.com> wrote:

> Hi all,
> My team is using Cassandra as our database. We have one question as below.
> As we know, the row with the some partition key will be stored in the some
> node.
> But how many rows can one partition key hold? What is it depend on? The
> node's volume or partition data size or partition rows size(the number of
> rows)?
>  When one partition's data is  extreme large, the write/read will slow?
> Can anyone show me some exist usecases.
>  thanks!
>
>
>
>
>
>

Re: how many rows can one partion key hold?

[Jens Rantil <je...@tink.se>]

Also, note that repairs will be slower for larger rows and AFAIK also
require slightly more memory. Also, to avoid many tombstones it could be
worth to consider bucketing your partitions by time.

Cheers,
Jens

On Fri, Feb 27, 2015 at 7:44 AM, wateray <wa...@163.com> wrote:

> Hi all,
> My team is using Cassandra as our database. We have one question as below.
> As we know, the row with the some partition key will be stored in the some
> node.
> But how many rows can one partition key hold? What is it depend on? The
> node's volume or partition data size or partition rows size(the number of
> rows)?
>  When one partition's data is  extreme large, the write/read will slow?
> Can anyone show me some exist usecases.
>  thanks!
>
>
>
>
>
>


-- 
Jens Rantil
Backend engineer
Tink AB

Email: jens.rantil@tink.se
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Re: how many rows can one partion key hold?

[Jack Krupansky <ja...@gmail.com>]

As a general, rough guideline, I would suggest that a partition be kept
down to thousands or tens of thousands of rows, probably not more than 100K
rows per partition, and physical size kept to tens of thousands to hundreds
of thousands or maybe a few megabytes or ten megabytes maximum per
partition.

So, a partition with millions of rows or tens of megabytes is probably
going to stress Cassandra too heavily. Of course, all of this depends on
your actual data model and your actual data values and your actual access
patterns. For example, if each row might be very large blobs, then a fewer
number of rows would be warranted. Or if each row is very tiny, maybe even
using compact storage, then a much larger row count is feasible. And if you
are doing heavy updates, then tombstone generation and compaction become
issues, that would argue for a smaller partition size. And if you tend to
do a lot of repair, you want to keep your row count per partition down, but
not too tiny.

Moderation is the message - avoid the extremes, both too large and too
small. This is not a matter of absolute limits per se, but common sense and
operational efficiency. And unfortunately performance and capacity of
Cassandra are highly non-linear, as are the values of most data, so exact
prediction of size and performance, particularly Java heap pressure are
quite unpredictable and require a proof of concept even to determine rough
recommendations for your specific app.


-- Jack Krupansky

On Fri, Feb 27, 2015 at 1:44 AM, wateray <wa...@163.com> wrote:

> Hi all,
> My team is using Cassandra as our database. We have one question as below.
> As we know, the row with the some partition key will be stored in the some
> node.
> But how many rows can one partition key hold? What is it depend on? The
> node's volume or partition data size or partition rows size(the number of
> rows)?
>  When one partition's data is  extreme large, the write/read will slow?
> Can anyone show me some exist usecases.
>  thanks!
>
>
>
>
>
>