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From Anuj Wadehra <anujw_2...@yahoo.co.in>
Subject Re: Read Consistency
Date Tue, 23 Jun 2015 19:02:38 GMT
Thanks..So all of us agree that in scenario 1, data would be returned and that was my initial
understanding..



Anuj




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From:"Anuj Wadehra" <anujw_2003@yahoo.co.in>
Date:Wed, 24 Jun, 2015 at 12:15 am
Subject:Re: Read Consistency

M more confused...Different responses. .Anyone who can explain with 100% surity ?


Thanks

Anuj



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From:"arun sirimalla" <arunsirik@gmail.com>
Date:Wed, 24 Jun, 2015 at 12:00 am
Subject:Re: Read Consistency



Thanks good to know that.


On Tue, Jun 23, 2015 at 11:27 AM, Philip Thompson <philip.thompson@datastax.com> wrote:

Yes, that is what he means. CL is for how many nodes need to respond, not agree.


On Tue, Jun 23, 2015 at 2:26 PM, arun sirimalla <arunsirik@gmail.com> wrote:

So do you mean with CL set to QUORUM, if data is only on one node, the query still succeeds.


On Tue, Jun 23, 2015 at 11:21 AM, Philip Thompson <philip.thompson@datastax.com> wrote:

Anuj,

In the first scenario, the data from the single node holding data is returned. The query will
not fail if the consistency level is met, even if the read was inconsistent.


On Tue, Jun 23, 2015 at 2:16 PM, Anuj Wadehra <anujw_2003@yahoo.co.in> wrote:

Why would it fail and with what Thrift error? What if the data didnt exist on any of the nodes..query
wont fail if doesnt find data..


Not convinced..

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From:"arun sirimalla" <arunsirik@gmail.com>
Date:Tue, 23 Jun, 2015 at 11:39 pm
Subject:Re: Read Consistency

Scenario 1: Read query is fired for a key, data is found on one node and not found on other
two nodes who are responsible for the token corresponding to key.


You read query will fail, as it expects to receive data from 2 nodes with RF=3



Scenario 2: Read query is fired and all 3 replicas have different data with different timestamps.


Read query will return the data with most recent timestamp and trigger a read repair in the
backend .


On Tue, Jun 23, 2015 at 10:57 AM, Anuj Wadehra <anujw_2003@yahoo.co.in> wrote:

Hi,


Need to validate my understanding..


RF=3 , Read CL = Quorum


What would be returned to the client in following scenarios:


Scenario 1: Read query is fired for a key, data is found on one node and not found on other
two nodes who are responsible for the token corresponding to key.


Options: no data is returned OR data from the only node having data is returned?


Scenario 2: Read query is fired and all 3 replicas have different data with different timestamps.


Options: data with latest timestamp is returned OR something else???


Thanks

Anuj


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-- 

Arun 





-- 

Arun 

Senior Hadoop/Cassandra Engineer

Cloudwick



2014 Data Impact Award Winner (Cloudera)

http://www.cloudera.com/content/cloudera/en/campaign/data-impact-awards.html






-- 

Arun 

Senior Hadoop/Cassandra Engineer

Cloudwick



2014 Data Impact Award Winner (Cloudera)

http://www.cloudera.com/content/cloudera/en/campaign/data-impact-awards.html



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