I have been doing a bit of preparation/planning for the upcoming merge of MySQL 5.6. I think the 5.6 merge (and 5.5 merge) is very important for MariaDB. There is much stuff in there that we really need to make available to our users (and probably some better left out). If we fail to keep the merges going, it will leave the community in a very sorry situation; I do not see anyone else stepping up to this task. My idea is that we could merge MySQL 5.6 piece-by-piece. Several other developers mentioned this idea at the Athens meeting: - It makes it much easier to selectively merge or not merge stuff. For example there are probably large chunks of optimiser changes that we do not want to merge (or maybe merge only the testcases for). On the other hand we probably want all InnoDB stuff. - I am hopeful it makes the merge much more managable when done in smaller pieces. Large reorganisations of code (header refactoring, copyright changes) should be easier when not intermixed with other changes. Merges from MySQL 5.5 -> MySQL 5.6 are probably also easier to deal with when done in isolation (I assume we can get conflicts for these, though we already have the equivalent changes in MariaDB 5.5). - Easier to share the task between developers. One developer can do a single piece in a few days, then pass the baton when he needs to switch to other tasks (or just gets tired). Complex merges of large feature pushes can be null-merged to allow main merge to progress, and in parallel another developer can work on reworking the patch into the MariaDB code. For some changes I think we will even be able to do the actual merge in parallel. - Easier to plan and understand how far the merge is progressing. Eg. if we merge M weeks worth of 5.6 pushes every N days, that allows to estimate when we will catch up with Oracle development - Easier debugging of test failures; by keeping the trees green between pieces merged, new test failures will be known to be caused by relatively smaller sets of changes, simplifying debugging. I have done some work to facilitate this kind of piecewise merge. As it turns out, it is not trivial to determine suitable pieces to merge. Oracle developers use no discipline for the direction they do merges in, so the sequence of pushes into lp:mysql-server ("trunk") is not immediately apparent. So I took the time to reconstruct the list of pushes from reading through the history; this was not overly hard to do. I next wrote a script that scans the history based on this list of pushes, and further annotates each push with some useful information: - Size of diff for the patch - Number of changesets merged (if a merge) - Mark if this is a merge from MySQL 5.5 - One-line short comment for the push, either hand-crafted for selected items, or else extracted from the commit message. - Revision ID (including developer info) It should be fairly simple to scan this list from the bottom, collecting chunks of related or manageable pushes and merging them as one piece. Eg. A sequence of small pushes could be merged as one, or a sequence of pushes by one developer, or a single large feature push. Here is an example extract of such an annotated list: 0 2* tor.didriksen@oracle.com-20111101065343-ha3d79h1ayk9j7x9 [5.5] Null merge from 5.1/5.5 13 andrei.elkin@oracle.com-20111031135232-q13pfsaieo8ujekj Minor test adjustment 791 alexander.nozdrin@oracle.com-20111031115220-01la8vj7ssmcm0mc Bug#61392 0 2* tor.didriksen@oracle.com-20111031091354-8p6s03s1zxerrp8p [5.5] Null merge Bug#12406055 from 5.1/5.5 5380 15 jorgen.loland@oracle.com-20111031081122-dnufl9r4li0i3ni6 [opt] Larger merge from optimiser tree 134 2* andrei.elkin@oracle.com-20111028212219-cdcuh37i70k9o4ms [5.5] Merge Bug#56299 (?) from 5.5 451 2 andrei.elkin@oracle.com-20111028130851-mz4p2mg28y14wb7k merge from trunk to local tree. 43 sergey.glukhov@oracle.com-20111028094528-enre87osw9u4qjy7 [opt] Bug#32254 post-merge fix (optimiser) 48 tor.didriksen@oracle.com-20111028092548-a3gjubgmwuhdunfj Bug#11747423 post-merge fix 114 tor.didriksen@oracle.com-20111028091835-xqavfrxkc50gbsxq "Default value for sort_buffer_size changed from 2M to 256K" The first column is diff size, the second is number of changesets merged (or empty for non-merge changesets). A "*" marks pushes that are only merges from MySQL 5.5. I pushed the script to lp:mariadb-tools, in /mysql-5.6-merge-stuff/. It also includes the full output in 5.6-annotated.txt (it takes 15-20 minutes for bzr to chew through the history on a fast multi-core machine). I hope this will be useful for the merge. Comments/suggestions/questions very welcome! - Kristian.