Comments on: Coherence Key HOWTO

By: Patrick Peralta

Patrick Peralta — Wed, 27 Mar 2013 18:32:49 +0000

The console is converting your numbers to int. Try including an extra space in front of your number to make it a String; i.e. get 5 instead of get 5.

By: Anu

Anu — Wed, 27 Mar 2013 02:34:32 +0000

I tested with some sample strings what I found was

When the key is of type string and it contains alphabets or alphanumeric characters, the values are getting retrieved correctly.

But if the key is of type String and the value is only numbers the values are not getting retrieved.

What is the reason for this?

By: Anu

Anu — Wed, 27 Mar 2013 01:29:15 +0000

Map (ele): list
2222222 =
200:20:2:2:1:1:Thu Feb 02 00:00:00 2012:2:Thu Feb 02 00:00:00 2012:Thu Feb 02 00:00:00 2012

GC2 =
200:20:2:2:1:1:Thu Feb 02 00:00:00 2012:2:Thu Feb 02 00:00:00 2012:Thu Feb 02 00:00:00 2012

Map (ele): get GC2
200:20:2:2:1:1:Thu Feb 02 00:00:00 2012:2:Thu Feb 02 00:00:00 2012:Thu Feb 02 00:00:00 2012

Map (ele): get 2222222
null

I have included the key in the equals() and hashcode() method. please tell me what is going wrong

By: Patrick Peralta

Patrick Peralta — Tue, 24 Apr 2012 19:47:31 +0000

This is correct Ashish – the associated key does not need to be physically present in the cache in order for affinity to work for a given entry.

By: Ashish Garg

Ashish Garg — Tue, 24 Apr 2012 18:23:46 +0000

On the similar question related to affinity just wanted to clear one doubt. The key affinity is based on the hash of the parent key not whether the parent key is present in the cache at that time.

Just to add an example let say Key B is associated with Key A. Now let say we had a parallel cache loader which first loads the Key B. So Key will be stored in the partition based on associated key details. Also when Key A is loaded it will fall in the same partition as that of its associated key B.

By: Patrick Peralta

Patrick Peralta — Tue, 10 Apr 2012 15:37:18 +0000

Great question! We do deserialize on the server to identify the association information. However, in 3.7.1 we added a feature to identify partition information in the binary itself so that .NET and C++ applications no longer require a corresponding Java key on the server side in order to use affinity. See http://docs.oracle.com/cd/E24290_01/coh.371/e22839/net_intobjects.htm under section “Deferring the Key Association Check” for details.

By: Ashish Garg

Ashish Garg — Tue, 10 Apr 2012 14:30:38 +0000

Very interesting post, how does this work in case of key affinity. As we need to de serialize the key to identify the association information.

By: Patrick Peralta

Patrick Peralta — Tue, 31 May 2011 02:01:51 +0000

RJW: this is absolutely correct! It doesn’t happen too often but I have seen it before. It can be very confusing if you don’t understand how Java serialization works internally.

By: Rjw

Rjw — Mon, 30 May 2011 10:31:08 +0000

One easy way to screw this up is to use java serialization or any serialisation that uses stream back references for reference equals objects. Because then your serialised form is dependent on whether your contents are interned. Eg a simple pair of integer (1,1) could end up having an inconsistent binary form if the 1 objects are reference equals. So, use EL or POF for keys, and no tricks.

By: Ashwin Jayaprakash

Ashwin Jayaprakash — Tue, 10 May 2011 20:15:14 +0000

This is a pretty common problem. I too had written about something similar a while ago – http://javaforu.blogspot.com/2009/12/primary-key-object-under-appreciated.html