incubator-cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From aaron morton <aa...@thelastpickle.com>
Subject Re: how to access data only on specific node
Date Fri, 17 May 2013 18:37:24 GMT
> And about range scan - as far as I understand, range scan could be done only with Order
Preserving Partitioner, but not with Random Partitioner.
Range scan can be used with any partitioner. 
If you use it with the RP the order of the rows will be ranged. 

Cheers

-----------------
Aaron Morton
Freelance Cassandra Consultant
New Zealand

@aaronmorton
http://www.thelastpickle.com

On 17/05/2013, at 7:19 PM, Sergey Naumov <sknaumov@gmail.com> wrote:

> Oh, I finally understand. As I read records one by one they aren't necessarily read from
a single node, so if I got 965 records out of 1000, some of them could be read from other
nodes which have all of 1000 records.
> 
> And about range scan - as far as I understand, range scan could be done only with Order
Preserving Partitioner, but not with Random Partitioner... It would be cool to have consistency
level of LOCAL to examine content of a local node for test purposes.
> 
> 
> 2013/5/17 aaron morton <aaron@thelastpickle.com>
> Are you using a multi get or a range slice ? 
> 
> Read Repair does not run for range slice queries. 
> 
> Cheers
> 
> -----------------
> Aaron Morton
> Freelance Cassandra Consultant
> New Zealand
> 
> @aaronmorton
> http://www.thelastpickle.com
> 
> On 15/05/2013, at 6:51 PM, Sergey Naumov <sknaumov@gmail.com> wrote:
> 
>>> see that RR works, but sometimes number of records have been read degrades. 
>> RR is enabled on a random 10% of requests, see the read_repair_chance setting for
the CF. 
>> 
>> OK, but I forgot to mention the main thing - each node in my config is a standalone
datacenter and distribution is DC1:1, DC2:1, DC3:1. So when I try to read 1000 records with
consistency ONE multiple times while connected to node that just have been turned on, I got
the following count of records read (approximately): 120 220 310 390 .... 950 960 965 !! 955
!! 970 ... If all other nodes contain 1000 records and read repair already delivered 965 records
to local DC (and so - local node), why sometimes I see degradation of total records read?
>> 
>> 
>> 
>> 2013/5/15 aaron morton <aaron@thelastpickle.com>
>>> see that RR works, but sometimes number of records have been read degrades. 
>> RR is enabled on a random 10% of requests, see the read_repair_chance setting for
the CF. 
>> 
>>>  If so, then the question is: how to perform local reads to examine content of
specific node?
>> You can check which nodes are replicas for a key using nodetool getendpoints
>> 
>> If you want to read all the rows for a particular row you need to use a range scan
and limit it by the token ranges assigned to the node. 
>> 
>> Cheers
>> 
>> -----------------
>> Aaron Morton
>> Freelance Cassandra Consultant
>> New Zealand
>> 
>> @aaronmorton
>> http://www.thelastpickle.com
>> 
>> On 14/05/2013, at 10:29 PM, Sergey Naumov <sknaumov@gmail.com> wrote:
>> 
>>> Hello.
>>> 
>>> I'am playing with demo cassandra cluster and decided to test read repair + hinted
handoff. 
>>> 
>>> One node of a cluster was put down deliberately, and on the other nodes I inserted
some records (say 1000). HH is off on all nodes.
>>> Then I turned on the node, connected to it with cql (locally, so to localhost)
and performed 1000 reads by row key (with consistency ONE). I see that RR works, but sometimes
number of records have been read degrades. Is it because consistency ONE and local reads is
not the same thing? If so, then the question is: how to perform local reads to examine content
of specific node?
>>> 
>>> Thanks in advance,
>>> Sergey Naumov.
>> 
>> 
> 
> 


Mime
View raw message