cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Dan Kuebrich <dan.kuebr...@gmail.com>
Subject Re: Cassandra Reads a little slow - 900 keys takes 4 seconds.
Date Wed, 31 Aug 2011 23:57:29 GMT
There might be some tuning you can do--key cache, etc--though I can't speak
to that in your particular case and with 50 column families you'd probably
run into pretty bad memory limits.

However, having found myself in a similar situation in the past, you might
consider experimentally trying different batch sizes on the # of rows (eg 1
request for 900 vs 9 for 100 each, etc).  This has helped me solve timeout
problems when retrieving "large" numbers of rows in the past and reduced
overall retrieval time.  I know that at least the pycassa client supports
this type of multiget out of the box.

On Wed, Aug 31, 2011 at 5:13 AM, Renato Bacelar da Silveira <
renatods@indabamobile.co.za> wrote:

> **
> Hi All
>
> I am running a query against a node with about 50 Column Families.
>
> At present One of the column families has 2,502,000 rows, each row
> contains 100 columns.
>
> I am searching for 3 columns specifically, and am doing so with Thrift's
> multiget_slice(). I prepare a statement with about 900 row  keys, each
> searching for a slice of 3 specific columns.
>
> My average time taken to return from the multiget_slice() is about 4
> seconds. I performed a comparative query in mysql, and the results
> were returned to me in 0.75 seconds or avarage.
>
> Is 4 seconds way too much time for Cassandra? I am sure this could
> be under 1 second, like MySql.
>
> I have resized the Thrift transport size to just 1MB so to not encounter
> any timeouts, as noted if you push too many queries through. Is this
> a correct assumption?
>
> So is it too much to push 900 keys in a multiget_slice() at once? I read
> that it does a concurrent fetch. I can understand threads racing for
> cycles, causing waits, but somehow I think I am wrong somewhere.
>
> Regards to ALL!
>
>
>
> Renato da Silveira
> Senior Developer
> www.indabamobile.co.za
>
>
>
> --
>

Mime
View raw message