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From Sergey Naumov <sknau...@gmail.com>
Subject Re: how to access data only on specific node
Date Fri, 17 May 2013 07:19:52 GMT
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.
>>
>>
>>
>
>

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