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From Kamal C <kamaltar...@gmail.com>
Subject Re: How to retrieve data from Collocated Cache with Simple Key
Date Wed, 08 Jun 2016 11:36:31 GMT
In my app, I'm trying to replace the existing ehcache implementation to
Ignite caches.

Using Affinity Collocation, I've collocated the data in the caches which are
accessed together. In many places, I've only SIMPLE key to retrieve the
data from the caches. (e.g. Retrieval from Person cache with only name)

In `put` operation, we have full object to insert so construction of
PersonKey /
 AffinityKey is not a problem. But, during `get` operation, we may have
only
the simple key to retrieve data.

I understand that Ignite looks data only in the partition specified by the
AffinityFunction computed on AffinityKey. Can I force Ignite to look for
data
on all the local cache partitions in the node ?



On Tue, Jun 7, 2016 at 10:38 AM, Denis Magda <dmagda@gridgain.com> wrote:

> 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>
> wrote:
>
>> I am sorry for mistake Kamal...
>> On Jun 6, 2016 3:34 PM, "Kamal" <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
>>> 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>
>>> Person.java
>>> <http://apache-ignite-users.70518.x6.nabble.com/file/n5452/Person.java>
>>>
>>>
>>>
>>>
>>> --
>>> View this message in context:
>>> http://apache-ignite-users.70518.x6.nabble.com/How-to-retrieve-data-from-Collocated-Cache-with-Simple-Key-tp5452.html
>>> Sent from the Apache Ignite Users mailing list archive at Nabble.com
>>> <http://nabble.com>.
>>>
>>
>
>

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