I agree that we shouldn't wait too long before merging the branch. We are targeting to have basic queries working within a month from now and will definitely propose to merge the branch back into trunk at that point. We will limit the scope of the work on the branch to just a few operators and primitive datatypes. Does that sound reasonable?
regards jitendra On Wed, Apr 3, 2013 at 9:03 PM, Namit Jain <nj...@fb.com> wrote: > There is no right answer, but I feel if you go this path a long way, it > will be very difficult > to merge back. Given that this is not a new functionality, and improvement > to existing code > (which will also evolve), it will become difficult to maintain/review a > big diff in the future. > > I haven't thought much about it, but can start by creating the high-level > interfaces first, and then > going from there. For e.g.: create interfaces for operators which take in > an array of rows instead of > a single row - initially the array size can always be 1. Now, proceed from > there. > > What makes you think, merging a branch 6 months/1 year from now will be > easier than working on the > current branch ? > > Having said that, both approaches can be made to work - but I think you > are just delaying the > merging work instead of taking the hit upfront. > > Thanks, > -namit > > > > On 4/4/13 2:40 AM, "Jitendra Pandey" <jiten...@hortonworks.com> wrote: > > > We did consider implementing these changes on the trunk. But, it would > >take several patches in various parts of the code before a simple end to > >end query can be executed on vectorized path. For example a patch for > >vectorized expressions will be a significant amount of code, but will not > >be used in a query until a vectorized operator is implemented and the > >query > >plan is modified to use the vectorized path. Vectorization of even basic > >expressions becomes non trivial because we need to optimize for various > >cases like chain of expressions, for non-null columns or repeating values > >and also handle case for nullable columns, or short circuit optimization > >etc. Careful handling of these is important for performance gains. > > > > Committing those intermediate patches in trunk without stabilizing them > >in a branch first might be a cause of concern. > > > > A separate branch will let us make incremental changes to the system so > >that each patch addresses a single feature or functionality and is small > >enough to review. > > We will make sure that the branch is frequently updated with the > >changes > >in the trunk to avoid conflicts at the time of the merge. > > Also, we plan to propose merger of the branch as soon as a basic end to > >end query begins to work and is sufficiently tested, instead of waiting > >for > >all operators to get vectorized. Initially our target is to make select > >and > >filter operators work with vectorized expressions for primitive types. > > > > We will have a single global configuration flag that can be used to > >turn > >off the entire vectorization code path and we will specifically test to > >make sure that when this flag is off there is no regression on the current > >system. When vectorization is turned on, we will have a validation step to > >make sure the given query is supported on the vectorization path otherwise > >it will fall back to current code path. > > > > Although, we intend to follow commit then review policy on the branch > >for > >speed of development, each patch will have an associated jira and will be > >available for review and feedback. > > > >thanks > >jitendra > > > >On Tue, Apr 2, 2013 at 8:37 PM, Namit Jain <nj...@fb.com> wrote: > > > >> It will be difficult to merge back the branch. > >> Can you stage your changes incrementally ? > >> > >> I mean, start with the making the operators vectorized - it can be a for > >> loop to > >> start with ? I think it will be very difficult to merge it back if we > >> diverge on this. > >> I would recommend starting with simple interfaces for operators and then > >> plugging them > >> in slowly instead of a new branch, unless this approach is extremely > >> difficult. > >> > >> > >> Thanks, > >> -namit > >> > >> On 4/3/13 1:52 AM, "Jitendra Pandey" <jiten...@hortonworks.com> wrote: > >> > >> >Hi Folks, > >> > I want to propose for creation of a separate branch for HIVE-4160 > >> >work. This is a significant amount of work, and support for very basic > >> >functionality will need big chunks of code. It will also take some > >>time to > >> >stabilize and test. A separate dev branch will allow us to do this work > >> >incrementally and collaboratively. We have already uploaded a design > >> >document on the jira for comments/feedback. > >> > > >> >thanks > >> >jitendra > >> > > >> > > >> >-- > >> ><http://hortonworks.com/download/> > >> > >> > > > > > >-- > ><http://hortonworks.com/download/> > > -- <http://hortonworks.com/download/>
