Hello guys, - jOOQ's main mission is to model SQL as an internal domain specific language in Java, and to ease the "JDBC pain". - jOOQ's secondary mission is to model a database's tables and records and other artefacts in a typesafe way.
Now, the "jOOQ CRUD API" is a nice side-effect of having an active-record or ADO.net like model of the underlying database tables. This model does act like a cache, just like JDBC ResultSets, JPA entities, .NET EntityFramework entities and many other database resource models "cache" data from the underlying database. Now, I completely agree that jOOQ shouldn't assume or even impose a transactional model from the many possible models. This is why I said that these things have to be done very carefully - if they're going to be done at all. I think that improving the CRUD API by adding transaction listeners could be a viable way to solve Ryan's problems in the future. But just having a couple of "awesome" (thanks Ryan) features is not a compelling enough reason to introduce this kind of complexity. Over the time, I'm collecting use-cases for introducing a generic transaction model, but it is certainly not a priority for jOOQ 3.0, 3.1 and other early 3.x versions, as I don't have a clear view on the problem domain, yet. As for optimistic locking, I do agree with Joachim. I'm not 100% convinced that it is implemented in the right way (yet, i.e. generically covering all use cases). It covers a lot of use-cases, though. And the ones that are missing can probably be added in the future. > [Ryan] I guess what I mean is, we seem to be thinking down a path that in > distinctly different from the core Jooq focus and it would seem necessary to > draw a line somewhere Yes, drawing a line is tough, as the short-term added value for users is often very tempting. Another area where this gets challenging is the mapping of Result / Record to POJOs. The point here is: jOOQ may always need to draw new lines. While the main mission is very clear and finite in scope, the secondary mission is not. It is open-ended and it should be debated again and again on this user group. jOOQ's internals have a very high degree of cohesion, meaning that all the features closely interact together. This is a good sign, and an effect of having added features slowly, after careful consideration (features, which aren't low-hanging fruit). Be assured that a transaction model will be added *very* slowly, if it is added at all. > [Ryan] Except in > ADO.net you work on a "table"/"view" level rather than record level. Anyway, > 2 separate projects... Funny, I had just recently thought about .store(), .delete(), .refresh() methods on Result, performing batch operations under the hood... Do you see anything worth implementing in jOOQ? Note, that updatable results are on the roadmap: https://github.com/jOOQ/jOOQ/issues/1846 Other nice ideas? Cheers Lukas 2013/2/24 Ryan How <[email protected]>: > Hi Jo, > > It almost seems like an entire project on it's own that has a different > focus than Jooq. Apart from the couple of methods (.store(), .delete() and > .refresh()), then Jooq doesn't really do anything too "smart" (it only does > "awesome"). And I think that works really well, you can use it just like > SQL, but much better integration with Java!. It makes it easy to learn, work > in a predictable manner and just provides benefits!. I haven't really found > a drawback yet, you can even just resort back to executing SQL if you want!, > or part of a statement in SQL. > > So it is like the Jooq CRUD API (I'm not quite sure what to call this part > of Jooq, is that a good name?), gives a little taste of a whole new world of > possibilities that can be built on top of JOOQ. Maybe it should come under a > different project and then can be built and maintained separately. But it > seems it still needs to tightly integrate with JOOQ too. > > It almost seems if it was going as far as to provide support for all the > different transaction models listed, it might as well handle validation and > plugging in other things, such as logging changes (audit trail) and things > like that? Why not put a cache in there too so then you can have the > permanent-sync case. > > I guess what I mean is, we seem to be thinking down a path that in > distinctly different from the core Jooq focus and it would seem necessary to > draw a line somewhere. If the core Jooq could provide the necessary hooks > and database integration, then these things could be plugged in to support > any desired use case without Jooq itself becoming too specific to one model. > > On a side note, does Jooq and the "crud" operations in any way remind you of > Linq and Ado.net ?, I haven't used them for a while, but the ADO.net > datatable is a bit like the Jooq Result and Record objects, where you can do > changes, it tracks those changes, then you can store the result. Except in > ADO.net you work on a "table"/"view" level rather than record level. Anyway, > 2 separate projects... > > Thanks, Ryan > > > > > On 21/02/2013 8:40 PM, Durchholz, Joachim wrote: >> >> I'm having similar thoughts as Ryan. >> >> Let me ramble a bit; I'm not really sure how well this fits with the >> direction Jooq is heading. I hope it helps "stepping back from the drawing >> board" and taking a look from a broader perspective - then maybe it doesn't. >> There's also the caveat that I have been unable to follow all the details >> of the discussion, so I may be missing important details or beating a dead >> horse. My apologies for that. >> That said, I hope it's more useful than distracting. Feel free to ignore. >> >> Tailoring the store operation to a specific use case is making me very >> nervous; I've been finding time and again that my transaction model doesn't >> quite fit the model the library designer had in mind. >> I suspect that this is partly due to the fact that as soon as you have a >> cache for the purpose of avoiding unnecessary UPDATEs, you also get >> optimistic locking for free, so you model the entire transaction model >> around optimistic locking. Which has the unfortunate side effect that all >> transaction models that do not use optimistic locking will have less >> support. >> >> So... I'm thinking about the transactional models I have been seeing and >> using. >> >> One model is the classic pessimistic locking (PL) model. >> It's the one that databases support out of the box; other transactional >> models are built on top of it. >> It's unsuitable for online processing if a transaction can run longer than >> a handful of seconds. >> It's also surprisingly unsuitable for anything that runs longer than about >> four hours, because it (a) accumulated a gigantic heap of rollback log and >> (b) if you need to rollback, you usually end up with having a failed batch >> run and not enough time to retry. >> The gist of all this is that while PL is the best, people have always been >> splitting PL transactions into smaller, shorter transactions, almost since >> RDBMSes exist. >> >> There's the idempotent transaction model. You run mostly nontransactional, >> but you make sure that each processing step can be repeated without ill >> effect, and that failure at any point won't damage the data. Essentially, >> you read the data but don't worry about whether there are any concurrent >> updates, and only the insert/update/delete operations need to run in a PL >> transaction (and sometimes even that isn't strictly required, the RDBMS's >> internal data structures would probably need transactional protection but >> writing inconsistent data can easily be corrected by rerunning the >> transaction). >> This works well for all processing steps that transform some constant data >> into some other, non-overlapping data. >> You need tight control over caching for this model: Some data you want to >> keep cached right at the beginning of the batch run until it is finished >> (configuration data that doesn't change except under administrator >> supervision). Some data you do not want to even see a cache: the bulk rows >> that are streamed through the update process. Some data you want to cache >> for a while and then throw away: information about a group of data (say, all >> data relating to a specific building while you're iterating over the data on >> the wares stored there and collect some statistics). >> >> Another model is the read-process-write with optimistic locking >> transaction. You read everything in one PL transaction, process the data, >> and write in a different PL transaction; you apply some clever tricks to >> fail when this would end overwriting data that has been modified by others. >> This is a very hairy approach: Sometimes, you want to fail when just the >> fields being overwritten have been modified elsewhere (e.g. customer name); >> sometimes, you want to fail if some other fields in the same record were >> modified (don't overwrite just the house number if somebody else modified >> the street name); sometimes, you want to fail if a record in a different >> table was updated (don't update the new price sum in the order record if >> some other order detail was modified - you might have to apply a different >> discount scheme now). >> Ultimately, it's the call of the application developer what kinds of >> changes might have to be checked before an update can go through. Just >> calling UPDATE with expected old values in the WHERE condition, then >> counting how many records were actually modified, is an excellent trick, but >> it's not covering all needs, just the most basic one. >> >> Then there's read-process-read-process-write model with optimistic >> locking. It's not imposing any additional requirements on the database >> library I think, it's just that the application programmer needs to be aware >> that the data he's working with might be outdated. >> >> Then there's the cache-indefinitely case. You read some data such as the >> list of company locations, which is never going to be modified except under >> administrator control who'll manually flush any cache and tell J2SE >> application users to restart their clients so they get a fresh copy of the >> cache. Automation is possible but runs through extra channels that the DB >> lib isn't aware of. >> >> Then there's the permanent-sync case. The application side gets notified >> of changes in any records that it has available locally. This isn't really >> different than optimistic locking, except that the optimistic locking >> exception might fly earlier. In the read-process-read-process-write case, it >> might avoid some exceptions. The downside is that it's entirely >> nonstandardized and very hard to implement. On the plus side, the entire >> data movement between application and database is automated and can be >> optimized; essentially, you're running (or faking, if you will) a database >> cluster where the application is keeping some records in the form of a Java >> object. >> It's the thing every developer wants and nobody gets :-) >> >> What I'm after is that I wouldn't want Jooq to support a specific >> transactional model preferentially. This runs the risk of less support for >> the other models. >> It's my main gripe about Hibernate, which works really well for >> read-process-write-with-optimistic-lock but sucks at every other model. I'm >> really worried that Jooq is about to enter the same kind of slippery slope, >> though maybe with a different transactional model. >> >> Just my 0.02 cents. >> >> Regards, >> Jo >> > > > -- > You received this message because you are subscribed to the Google Groups > "jOOQ User Group" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/groups/opt_out. > > -- You received this message because you are subscribed to the Google Groups "jOOQ User Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/groups/opt_out.
