Hi Romain,
I'm a bit confused cause initially you saying that
/The value is computed on first access and it is then cached
/and then you add that
/One constraint is that the computed value is not serializable. //
/
Ignite won't be able to store a value of cache if serialization is not
supported for it by some reason.
Please clarify here. Probably I'm missing something from your description.
--
Denis
On 12/16/2015 6:21 PM, Andrey Kornev wrote:
Romain
I suggest you be very careful using the invoke() functionality. As explained in
this posting (and the follow-ups)
http://mail-archives.apache.org/mod_mbox/ignite-dev/201511.mbox/%3CSNT147-W14D2736E1374450B685721CF000%40phx.gbl%3E
the correct usage of the invoke() may be difficult, to put it politely.
@Denis Very briefly, the use case is "conditional re-compute". There is a
pretty expensive computation that needs to be applied to each entry on demand. The value
is computed on first access and it is then cached along with the current version of the
cache entry. The value must be recomputed on next access only if the entry has been
modified.
If anyone has a better idea how to achieve something like that, please do
share! One constraint is that the computed value is not serializable.
Cheers
Andrey
Subject: Re: Missing ways to get access to Ignite CacheEntry
To: [email protected]
From: [email protected]
Date: Wed, 16 Dec 2015 16:11:48 +0300
Romain,
If it's implemented this way for now it doesn't mean that we can't
enhance the API for other use cases ;)
As I said presently it's supported for limited number of methods mostly
by performance reasons.
Please go ahead and try invoke/invokeAll and if it doesn't work fine for
you we can keep discussing what to do next.
Regards,
Denis
On 12/16/2015 1:53 PM, Romain Gilles wrote:
Hi Denis,
Thanks for you replay. And sorry to not double check it before. I see that
if I want to work with CacheEntry, I need to use the invoke method in order
to return the CacheEntry. This is the way I should do it. It sounds like
complicated for "just" getting an entry. But if you say this is the way I
will do it like that. I was just think that it could be a common use case
and therefore provide it as a shortcut.
Thanks,
Romain.
Le mer. 16 déc. 2015 à 11:34, Denis Magda <[email protected]> a écrit :
Hi Romain,
As the current documentation of org.apache.ignite.cache.CacheEntry
states it's possible to get a reference to CacheEntry and its version
only for methods that are executed over local data set stored on a node.
Among such methods are invoke & invokeAll and randomEntry.
You probably can get a CacheEntry and its non null version when a cache
iterator is in use but the version will be 'null', as far as I remember,
for those entries that are loaded from remote nodes.
Presently Ignite doesn't transfer the version from remote nodes as a
part of response by perform reasons.
Please elaborate more on your particular use case and what API you would
like to add in order to support it.
--
Denis
On 12/16/2015 12:58 PM, Romain Gilles wrote:
Hi Igniters,
I'm looking for a way to get access to the Ignite CacheEntry. For now
this
is the ways I found:
- Through the queris
- Through jsr 107 Cache Iterable
- Through jsr 107 Cache itterator
- Through IgniteCache::randomEntry()
If I remember correctly it was possible to get the CacheEntry from a
given
key in old version of gridgain community
version: GridCacheProjection::entry(K key) GridCacheEntry<K,V>
I think it could be a good to introduce this feature at IgniteCache
level.
Or maybe there is an other way to do it.
Thanks,
Romain.
