Hi Julian, Thanks for the response.
Yes indeed, it looks like there will be several Samza specific push-downs and RelNodes. I'm still trying to understand how conventions work and what is there for Samza. But I'm sure we will need a Samza specific convention as we grow. Milinda On Wed, Mar 18, 2015 at 4:53 PM, Julian Hyde <[email protected]> wrote: > ProjectableTable and ProjectableFilterableTable are compromises. They make > it easy for someone to write a Calcite adapter for a data source, and > perform the most common push-downs. 80% of the value for 20% of the effort. > > I thought it was worth pushing down filter expressions (e.g. x > 5 AND y > is null) but I didn’t think it was worth pushing down projections. The > ProjectableFilterableTable.scan API reflects this. > > If someone is an expert in Calcite, and has a data source that is capable > of doing significant computation (e.g. covers a lot of the built-in SQL > functions, user-defined functions, aggregation…) then they should build a > “real” adapter. They will also need to write their own RelNodes, push-down > rules, and probably their own convention. FWIW I think Samza is in that > category. > > Julian > > > On Mar 18, 2015, at 7:51 AM, Milinda Pathirage <[email protected]> > wrote: > > > Hi Julian, > > > > I am trying to understand why Project and Scan merging is avoided when > > there are projections which are RexCalls. Is this a purely implementation > > related rule (such as separation of concerns or keeping scan as simple as > > possible) or is there any theoretical background for this. > > > > I am asking this because I discovered that Project#getMapping returns > null > > when there are RexCalls in the projection which prevent > ProjectableScanRule > > from transforming the logical expression tree. > > > > Thanks in advance, > > Milinda > > > > -- > > Milinda Pathirage > > > > PhD Student | Research Assistant > > School of Informatics and Computing | Data to Insight Center > > Indiana University > > > > twitter: milindalakmal > > skype: milinda.pathirage > > blog: http://milinda.pathirage.org > > -- Milinda Pathirage PhD Student | Research Assistant School of Informatics and Computing | Data to Insight Center Indiana University twitter: milindalakmal skype: milinda.pathirage blog: http://milinda.pathirage.org
