Thanks Russel for the reply .
After going through all the APIs I too reached the same opinion. 1)Simultaneous
multiple fetch and 2)MapReduce. However, simultaneous access would make the
fetch very slower and it doesnt look efficient ( since there are threads
spawned for each key and fetching say, 10K records might be an over head) let
me know if I miss something here and that I shoudl not be concerned. My worry
is not the procedure to spawn so many worker threads, but the number of
connections they open and close and the performance overhead, thereby
I tried the map reduce in similar way that you mentioned. For weird reasons, it
throws Java Heap memory exception and dies.
MapReduceResult result = client.mapReduce() .addInput("goog","2010-01-04")
.addInput("goog","2010-01-05") .addInput("goog","2010-01-06")
.addInput("goog","2010-01-07") .addInput("goog","2010-01-08") .addMapPhase(new
NamedJSFunction("Riak.mapValuesJson"), true) .execute();
I used the same format as above mentioned in
https://github.com/basho/riak-java-client page. I tried with and without the
addMapPhase method, but in vain. Am I missing something here? Is there a
prerequisite to use this code?
I also see that the above methods works only for IRiakClient. Until now I have
been using RiakClient. Only to access these methods. I am using IRiakClient.
Does that have any significance? way to access/ configure IRiakClient/
Mapreduce. This is the only place I need the map reduce,
and throughout my code, i just store and fetch key values.
I dont seem to get the answers in the forums or documents. If there are any,can
you please point? Thanks again.
Suresh C Nair
________________________________
From: Russell Brown <[email protected]>
To: suresh chandran <[email protected]>
Cc: "[email protected]" <[email protected]>
Sent: Monday, November 28, 2011 7:14 PM
Subject: Re: Multiple keys to fetch in a Java client
On 28 Nov 2011, at 20:16, suresh chandran wrote:
May be I can make my statement clear :) I store my devices values in buckets
named after OS (say windows/ linux) with the device id's as keys. I want to
get the devices for a list of device ids . From what I see, the fetch API
signature takes in bucket name and key. (Client.fetch("windows", "D1"). Is
there a way where I can get Client.fetch("windows", <Collection fo keys>?
>
There is no multi-fetch from Riak right now. You can either fetch your
individual keys (serially on in parallel) or run a Map/Reduce. In most case the
Map/Reduce will be slower (though the API is simpler, I suppose.)
Use IRiakClient.mapReduce().addInput(bucket, key).addInput(bucket,
key2)…(repeat!) I guess this is ripe for a convenience method that takes (as
you suggest) addInputs(bucket, Collection<String> keys), so I'll add that to
the features list.
Or just fetch all your keys using fetch.
I guess it would be possible to add a bulk fetch API to the Riak Java Client
that spawns a configurable number of threads to fetch a bunch of keys in
parallel, but right now that is left as an exercise for the reader :)
Cheers
Russell
>Thanks
>Suresh C Nair
>
>
>________________________________
> From: suresh chandran <[email protected]>
>To: "[email protected]" <[email protected]>
>Sent: Monday, November 28, 2011 2:53 PM
>Subject: Multiple keys to fetch in a Java client
>
>
>HI,
>
>
>I am storing values of a devices under a particular OS. I want to fetch the
>list of all vallues, based on the key list. What I see if that, I can fetch
>the value one by one using the FETCH. Am using the HttpClient in Java. How do
>I go about this? Assume I am tryign to reach the same behavior like query that
>has "CONTAINS(key1, key2...). Is there a way to do this? or we can fetch the
>values only one by one. I do see that Map-reduce, makes use of the list fo
>keys, but am not sure if it is applicable in my case, as it ia simple
>fetch with collection of / list of keys.
>
>
>Thanks
>Suresh C Nair
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>
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