Hmm, are you sure John? I agree that the Objects won’t be in any object cache, but won’t the data be in the snapshot cache (just like EOF)?
On Wed, Mar 8, 2017 at 2:30 PM, John Huss <[email protected]> wrote: > Right > On Wed, Mar 8, 2017 at 3:16 PM Musall, Maik <[email protected]> wrote: > > > And unless I'm explictly creating a query cache somewhere in my > > application, > > I won't have one? > > > > > Am 08.03.2017 um 22:05 schrieb John Huss <[email protected]>: > > > > > > Unless you are using a query cache then running an ObjectSelect will > > always > > > give you fresh data from the DB. > > > On Wed, Mar 8, 2017 at 3:01 PM Musall, Maik <[email protected]> > > wrote: > > > > > >> Can someone confirm this? Will I always get fresh data from DB with an > > >> explicit query, or am I at risk being returned stale data from a > > >> context-local cache that doesn't even see changes that haven been > > recorded > > >> in the shared snapshot cache in the meantime, let alone in the > database? > > >> > > >> I'm still a bit puzzled and out of documentation about the question of > > how > > >> to control data freshness. Cayenne seems to be a bit different than > EOF > > in > > >> this regard, with it's multi-level caching. > > >> > > >> Maik > > >> > > >> > > >>> Am 24.02.2017 um 23:24 schrieb Markus Reich < > > [email protected] > > >>> : > > >>> > > >>> I think if you start a "standard" query it goes always against the > DB, > > >> this > > >>> would be the query cache but this is not implicit done, you have to > use > > >>> groups for that. > > >>> Object cache as I understand works behind the scenes, when you access > > >>> properties of you persistent entity with getters, then values where > > read > > >>> through the GraphManager from Cache. > > >>> Only OID Queries and RelationalQueries can get their data from cache. > > >>> Standard SelectQuery always runs a query on DB. But maybe I'm wrong > :-/ > > >>> > > >>> Musall, Maik <[email protected]> schrieb am Fr., 24. Feb. 2017 um > > >>> 23:14 Uhr: > > >>> > > >>>> Hi Lon, > > >>>> > > >>>> so with a context-local cache, you would still execute a regular > > query, > > >>>> but that query would not actually hit the database but the cache > would > > >>>> return the result instead? Is it like a result set per query SQL > > string > > >>>> which is cached? I don't really understand how those local caches > are > > >> keyed. > > >>>> > > >>>> If there is any Cayenne documentation explaining this which I > missed, > > >> I'd > > >>>> be happt to get a pointer to that. > > >>>> > > >>>> Maik > > >>>> > > >>>>> Am 24.02.2017 um 18:25 schrieb Lon Varscsak < > [email protected] > > >: > > >>>>> > > >>>>> I built something similar in EOF to local cache, so I think I can > > >> answer > > >>>> at > > >>>>> least part of the question. > > >>>>> > > >>>>> It’s not uncommon for me to have a complex set of queries to do > > >> something > > >>>>> like compute pricing on an order. Rather than having to maintain > > many > > >>>> tiny > > >>>>> caches or ivars with query results, all of my code executes queries > > to > > >>>> get > > >>>>> the data set it needs whenever the pricing calculation is called. > It > > >>>> makes > > >>>>> the code simpler, but gives you the performance of having stored > the > > >>>>> results yourself in an ivar (or dictionary). > > >>>>> > > >>>>> Add in EHCache and now you can control how long those objects live > > >>>> (rather > > >>>>> than the life of an ivar). If they get removed from cache due to > > cache > > >>>>> control settings, the next time through the code, it will refetch > > them > > >>>> but > > >>>>> I don’t have to be aware of this from a code perspective. > > >>>>> > > >>>>> Where I’m still hung up, is that it’s common for me to have many > > parts > > >> of > > >>>>> my code that are not aware of each other that display/operate on > the > > >> same > > >>>>> data, and I’m unsure how to update the cache (since there are > > multiple > > >>>>> local caches) in between those two components after commit (since > > >> change > > >>>>> propagation is turned off by default and even when on is in a > > separate > > >>>>> thread so I can’t assume the objects will be refreshed when I > need). > > >>>>> > > >>>>> -Lon > > >>>>> > > >>>>> On Fri, Feb 24, 2017 at 3:00 AM, Musall, Maik < > [email protected]> > > >>>> wrote: > > >>>>> > > >>>>>> Hi all, > > >>>>>> > > >>>>>> I'd like to extend this question a bit. I just read the entire > > >>>> performance > > >>>>>> tuning chapter again [1], and I'm a bit puzzled especially about > the > > >>>>>> ObjectContext's local caches, which Andrus also recommended to use > > in > > >>>> the > > >>>>>> "A way to refreshObject()" thread: > > >>>>>> > > >>>>>>> So instead of micro-optimizations with shared snapshot cache, you > > >>>> should > > >>>>>> use queries with cache groups and query cache. They get refetched > > >> when a > > >>>>>> cache group is flushed in response to an object commit. So > > technically > > >>>> you > > >>>>>> are not reusing the snapshot cache, but it really doesn't matter. > > The > > >>>>>> benefit you get in code simplicity, consistency, and often > > >> performance, > > >>>>>> always outweighs that. Besides this approach is cluster-friendly. > > >>>>>> > > >>>>>> Coming from EOF I grew the habit of frequently creating > short-lived > > >>>>>> ObjectContexts, so basically every page load uses it's own new > > >>>>>> ObjectContext to get fresh data from the shared global cache, > > because > > >>>> other > > >>>>>> users may have altered data between page loads. While working on a > > >>>> page, I > > >>>>>> have references to the objects that I need there anyway, so I > don't > > >>>>>> understand at all what that context-local cache mechanism should > do > > >> for > > >>>> me, > > >>>>>> unless that "create new contexts all the time" strategy is just > > plain > > >>>> wrong > > >>>>>> for Cayenne-based applications? > > >>>>>> > > >>>>>> And even if I would use a longer-lived ObjectContext for > something, > > >>>> where > > >>>>>> would that local cache get in effect? Either I have references to > > >>>> objects > > >>>>>> anyway, or I would need to refetch them, which would go through to > > the > > >>>>>> database, right? In what case would I get a benefit from a local > > >> cache? > > >>>> I > > >>>>>> didn't find answers to this in the Cayenne Guide. > > >>>>>> > > >>>>>> Thanks > > >>>>>> Maik > > >>>>>> > > >>>>>> [1] https://cayenne.apache.org/docs/4.0/cayenne-guide/ > > >>>>>> performance-tuning.html <https://cayenne.apache.org/ > > >>>>>> docs/4.0/cayenne-guide/performance-tuning.html> > > >>>>>> > > >>>>>> > > >>>>>>> Am 23.02.2017 um 09:43 schrieb Markus Reich < > > >>>> [email protected] > > >>>>>>> : > > >>>>>>> > > >>>>>>> Hi, > > >>>>>>> > > >>>>>>> I'm looking for a more detailed explaination of the caching > > >> mechanism, > > >>>> as > > >>>>>>> we are running a quite important and big web application with > > >> cayenne, > > >>>> I > > >>>>>>> want to fine tune, because we run in some performance issues. > > >>>>>>> > > >>>>>>> I only found this > > >>>>>>> https://cayenne.apache.org/docs/3.0/individual-object- > caching.html > > >>>>>>> > > >>>>>>> In 4.0 docu I can't find anything > > >>>>>>> > > >>>>>>> br > > >>>>>>> Meex > > >>>>>> > > >>>>>> > > >>>> > > >>>> > > >> > > >> > > > > >
