Right On Wed, Mar 8, 2017 at 3:16 PM Musall, Maik <m...@selbstdenker.ag> 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 <johnth...@gmail.com>: > > > > 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 <m...@selbstdenker.ag> > 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 < > markus.re...@markusreich.at > >>> : > >>> > >>> 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 <m...@selbstdenker.ag> 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 <lon.varsc...@gmail.com > >: > >>>>> > >>>>> 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 <m...@selbstdenker.ag> > >>>> 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 < > >>>> markus.re...@markusreich.at > >>>>>>> : > >>>>>>> > >>>>>>> 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 > >>>>>> > >>>>>> > >>>> > >>>> > >> > >> > >
