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From: Andrey Kornev <andrewkornev@hotmail.com>
To: "dev@ignite.apache.org" <dev@ignite.apache.org>
Subject: RE: Missing ways to get access to Ignite CacheEntry
Date: Wed, 16 Dec 2015 07:21:15 -0800
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In-Reply-To: <56716314.3050803@gridgain.com>
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Romain

I suggest you be very careful using the invoke() functionality. As explaine=
d in this posting (and the follow-ups)
http://mail-archives.apache.org/mod_mbox/ignite-dev/201511.mbox/%3CSNT147-W=
14D2736E1374450B685721CF000%40phx.gbl%3E
the correct usage of the invoke() may be difficult=2C to put it politely.

@Denis Very briefly=2C the use case is "conditional re-compute". There is a=
 pretty expensive computation that needs to be applied to each entry on dem=
and. 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.=20

If anyone has a better idea how to achieve something like that=2C 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: dev@ignite.apache.org
> From: dmagda@gridgain.com
> Date: Wed=2C 16 Dec 2015 16:11:48 +0300
>=20
> Romain=2C
>=20
> If it's implemented this way for now it doesn't mean that we can't=20
> enhance the API for other use cases =3B)
> As I said presently it's supported for limited number of methods mostly=20
> by performance reasons.
>=20
> Please go ahead and try invoke/invokeAll and if it doesn't work fine for=
=20
> you we can keep discussing what to do next.
>=20
> Regards=2C
> Denis
>=20
> On 12/16/2015 1:53 PM=2C Romain Gilles wrote:
> > Hi Denis=2C
> > Thanks for you replay. And sorry to not double check it before. I see t=
hat
> > if I want to work with CacheEntry=2C I need to use the invoke method in=
 order
> > to return the CacheEntry. This is the way I should do it. It sounds lik=
e
> > 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 ca=
se
> > and therefore provide it as a shortcut.
> >
> > Thanks=2C
> >
> > Romain.
> >
> > Le mer. 16 d=E9c. 2015 =E0 11:34=2C Denis Magda <dmagda@gridgain.com> a=
 =E9crit :
> >
> >> Hi Romain=2C
> >>
> >> 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 nod=
e.
> >> Among such methods are invoke & invokeAll and randomEntry.
> >>
> >> You probably can get a CacheEntry and its non null version when a cach=
e
> >> iterator is in use but the version will be 'null'=2C as far as I remem=
ber=2C
> >> 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 wou=
ld
> >> like to add in order to support it.
> >>
> >> --
> >> Denis
> >>
> >> On 12/16/2015 12:58 PM=2C Romain Gilles wrote:
> >>> Hi Igniters=2C
> >>> 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=2CV>
> >>> 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=2C
> >>>
> >>> Romain.
> >>>
> >>
>=20
 		 	   		  =

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