[infinispan-issues] [JBoss JIRA] (ISPN-5035) DeltaAware support for conditional operations

[Radim Vansa (JIRA)]

    [ https://issues.jboss.org/browse/ISPN-5035?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13026359#comment-13026359 ] 

Radim Vansa commented on ISPN-5035:
-----------------------------------

I'd assume that the code using cache.replace would look like
{code}
Foo oldFoo = cache.get("foo");
Foo newFoo = new Foo(oldFoo).addBar("bar");
boolean succeeded = cache.replace("foo", oldFoo, newFoo);
{code}
As during replication any DeltaAware command parameter is replaced by Delta, currently we would send cache.replace("foo", zero-delta, delta-with-bar) and get false since zero-delta does not match the object. I think that we should not produce the zero-delta from oldFoo (only the one with delta-with-bar), and the replace should work as if Foo did not implement DeltaAware.

Anyway, I don't think I would like to use DeltaAware for such use-case anyway. My concern is just that the API is not consistent.


> DeltaAware support for conditional operations
> ---------------------------------------------
>
>                 Key: ISPN-5035
>                 URL: https://issues.jboss.org/browse/ISPN-5035
>             Project: Infinispan
>          Issue Type: Feature Request
>          Components: Core
>            Reporter: Radim Vansa
>
> Current delta-aware approach is implemented only in PutKeyValueCommand and ApplyDeltaCommand. This implementation does not allow to execute conditional delta-aware commands - or rather it does not allow to return any kind of value (the condition itself can be implemented inside the delta).
> One use-case when this would be required is equivalent of AtomicLong.getAndIncrement(). Currently we can implement this using
> {code}
> Long previous;
> do {
>     previous = cache.get(key);
> } while (cache.replace(key, previous, previous + 1);
> {code}
> which requires at least two RPCs. With more generic interface, such as JCache's EntryProcessor this could be implemented using single RPC.
> (so, this JIRA is basically a request to native support for EntryProcessor)



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