Thank you for the explanation! Best regards, Zoltan
On Tue, Jan 28, 2020 at 5:58 PM Alan Gates <alanfga...@gmail.com> wrote: > I don't have answers to all of your questions, but I'll reply to the ones I > know or have opinions on. > > On Tue, Jan 28, 2020 at 6:20 AM Zoltan Chovan <zcho...@cloudera.com.invalid > > > wrote: > > > Hey, > > > > Additionally, I've been looking at TxnHandler and CompactionTxnHandler > > classes, these only use directSql, which makes testing any changes to > them > > quite difficult. Are there any plans to introduce JDO/Datanucleus in > those > > parts? > > > I didn't use JDO when I wrote this because an object model is a really bad > abstraction for transaction and locks. The solution for this is not to > move it into the object model but rather to move it out of constant > database operations and into something that will be faster and lighter > weight. I believe Olli Draese has some thoughts on how to do this, > something along the lines of an in memory cache for reads and a WAL for > writing out locks and transaction open, commit, abort. > > > > > Also how committed are we to Datanucleus as the JDO/ORM lib? Is there or > > were there any plans to switch? I know about Hibernate and MyBatis as > > possible alternatives. Sidenote: afaik Hibernate has LGPL license which > > might be a problem, is that correct? MyBatis on the other hand is Apache > > License 2.0. > > > LGPL excludes Hibernate as an option. > > > > > > I am aware that these changes would be quite enormous, but on the long > run > > it might give us better performance and testability, also most likely > > easier/quicker development in the related parts. My intention is to > start a > > discussion on the topic. > > > Given the huge impact this change would have on developers and the existing > user base, the expected benefit would have to be very large for it to make > sense to pay the cost. > > Alan. > > > > > What are your thoughts? > > > > Best regards, > > Zoltan > > > > [1] https://github.com/apache/hive/blob/master/pom.xml#L131 > > [2] http://www.datanucleus.org/documentation/products.html > > [3] > http://www.datanucleus.org/products/accessplatform_5_1/migration.html > > >
