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From Denis Magda <dma...@gridgain.com>
Subject Re: How to retrieve data from Collocated Cache with Simple Key
Date Tue, 07 Jun 2016 05:08:48 GMT
Hi Kamal,

There is no need to use any workaround like ScanQueries or iterators. You just need to use
a valid key to retrieve the data.
The valid key in your example is new AffinityKey<>(key, affray). It means that every
time you need to put or get a Person from the cache you need to use this kind of key where
“key” and “affray” will vary.

Also it’s not required to use AffinityKey instance all the time. You are free to create
your own implementation of a key

class PersonKey {

private int id;

@AffinityKeyMaped 
private int orgId;

//hash code and equals implementations are below
}

The ticket is created for NPE you got when were using a wrong key
https://issues.apache.org/jira/browse/IGNITE-3263

—
Denis

> On Jun 7, 2016, at 7:40 AM, Kamal C <kamaltarget@gmail.com> wrote:
> 
> Thanks for your response Vladislav. 
> 
> Both ScanQuery and Iterator traverses the whole cache to find the value. 
> It may not be suitable in my environment as there can be huge number of
> hits.
> 
> I understand that for fast retrieval `key-to-partition` mapping is done. 
> But, In AffinityKey documentation, it's specified that hashcode and equals
> methods are implemented based on simple key. 
> 
> * <p>
>  * Note that the {@link #equals(Object)} and {@link #hashCode()} methods
>  * delegate directly to the wrapped cache key provided by {@link #key()}
>  * method.
>  * <p>
> 
> On Mon, Jun 6, 2016 at 10:44 PM, Vladislav Pyatkov <vpyatkov@gridgain.com <mailto:vpyatkov@gridgain.com>>
wrote:
> I am sorry for mistake Kamal...
> 
> On Jun 6, 2016 3:34 PM, "Kamal" <kamaltarget@gmail.com <mailto:kamaltarget@gmail.com>>
wrote:
> Hi,
> 
>     I've gone through the affinity collocation[1] example to understand how
> data gets collocated across caches. In my example, I found that I'm not able
> to retrieve data from collocated cache with simple key.
> 
> I mean.
> 
> Cache<AffinityKey&lt;String>, Person> personCache = ..;
> personCache.get(new AffinityKey<>(key, affKey)); // returns value
> personCache.get(new AffinityKey<>(key)); // throws NPE
> 
> Exception in thread "main" java.lang.NullPointerException
>         at
> org.apache.ignite.cache.affinity.rendezvous.RendezvousAffinityFunction.partition(RendezvousAffinityFunction.java:428)
>         at
> org.apache.ignite.internal.processors.cache.GridCacheAffinityManager.partition(GridCacheAffinityManager.java:206)
>         at
> org.apache.ignite.internal.processors.cache.GridCacheContext.toCacheKeyObject(GridCacheContext.java:1801)
>         at
> org.apache.ignite.internal.processors.cache.distributed.dht.atomic.GridDhtAtomicCache.get(GridDhtAtomicCache.java:339)
>         at
> org.apache.ignite.internal.processors.cache.GridCacheAdapter.get(GridCacheAdapter.java:4650)
>         at
> org.apache.ignite.internal.processors.cache.GridCacheAdapter.get(GridCacheAdapter.java:1391)
>         at
> org.apache.ignite.internal.processors.cache.IgniteCacheProxy.get(IgniteCacheProxy.java:907)
>         at
> my.apache.ignite.examples.collocation.CacheCollocationExample.main(CacheCollocationExample.java:69)
> 
> In some scenarios, I have to fetch data from cache by simple key.
> 
> [1]: https://apacheignite.readme.io/docs/affinity-collocation <https://apacheignite.readme.io/docs/affinity-collocation>
> CacheCollocationExample.java
> <http://apache-ignite-users.70518.x6.nabble.com/file/n5452/CacheCollocationExample.java
<http://apache-ignite-users.70518.x6.nabble.com/file/n5452/CacheCollocationExample.java>>
> Company.java
> <http://apache-ignite-users.70518.x6.nabble.com/file/n5452/Company.java <http://apache-ignite-users.70518.x6.nabble.com/file/n5452/Company.java>>
> Person.java
> <http://apache-ignite-users.70518.x6.nabble.com/file/n5452/Person.java <http://apache-ignite-users.70518.x6.nabble.com/file/n5452/Person.java>>
> 
> 
> 
> 
> --
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<http://apache-ignite-users.70518.x6.nabble.com/How-to-retrieve-data-from-Collocated-Cache-with-Simple-Key-tp5452.html>
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> 


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