Taking a step back, what exactly is the proposal. Looking at the original message, I see
(1) Letting SQL take a dependency on Euphoria, sharing more code and taking advantage of the logical nesting of levels of abstraction. This makes sense to me. (2) Nesting the directories (but not the gradle targets or module names?). Here I'm not so sure about the benefit, especially vs. the cost. On Sat, Dec 1, 2018 at 8:38 AM Jan Lukavský <je...@seznam.cz> wrote: > > I think that the fact that SQL uses some other internal dependency > should remain hidden implementation detail. I absolutely agree that the > dependency should of course remain sdks-java-sql in all cases. > > Jan > > On 12/1/18 12:54 AM, Robert Bradshaw wrote: > > I suppose what I'm trying to say is that I see this module structure > > as a tool for discoverability and enumerating end-user endpoints. In > > other words, if one wants to use SQL, it would seem odd to have to > > depend on sdks-java-euphoria-sql rather than just sdks-java-sql if > > sdks-java-euphoria is also a DSL one might use. A sibling relationship > > does not prohibit the layered approach to implementation that sounds > > like it makes sense. > > > > (As for merging Euphoria into core, my initial impression is that's > > probably a good idea, and something we should consider for 3.0 at the > > very least.) > > > > On Fri, Nov 30, 2018 at 11:06 PM Jan Lukavský <je...@seznam.cz> wrote: > >> Hi Rui, > >> > >> yes, there are optimizations that could be added by each layer. The > >> purpose of Euphoria layer actually is not to reorder or modify any user > >> operators that are present in the pipeline (because it might not have > >> enough information to do this), but it can for instance choose between > >> various join implementations (shuffle join, broadcast join, ...) - so the > >> optimizations it can do are more low level. But this plays nicely with the > >> DSL hierarchy - each layer adds a little more restrictions, but can > >> therefore do more optimizations. And I think that the layer between SDK > >> and SQL wouldn't have to support SQL optimizations, it would only have to > >> support way for SQL to express these optimizations. > >> > >> Jan ---------- Původní e-mail ---------- > >> Od: Rui Wang <ruw...@google.com> > >> Komu: dev@beam.apache.org > >> Datum: 30. 11. 2018 22:43:04 > >> Předmět: Re: [DISCUSS] Structuring Java based DSLs > >> > >> SQL's optimization is another area to consider for integration. SQL > >> optimization includes pushing down filters/projections, merging or > >> removing or swapping plan nodes and comparing plan costs to choose best > >> plan. Add another layer between SQL and java core might need the layer to > >> support SQL optimizations if there is a need. > >> > >> I don't have a clear image on what SQL needs from Euphoria for > >> optimization(best case is nothing). As those optimizations are happening > >> or will happen, we might start to have a sense of it. > >> > >> -Rui > >> > >> On Fri, Nov 30, 2018 at 12:38 PM Robert Bradshaw <rober...@google.com> > >> wrote: > >> > >> I don't really see Euphoria as a subset of SQL or the other way > >> around, and I think it makes sense to use either without the other, so > >> by this criteria keeping them as siblings than a nesting. > >> > >> That said, I think it's really good to have a bunch of shared code, > >> e.g. a join library that could be used by both. One could even depend > >> on the other without having to abandon the sibling relationship. > >> Something like retractions belong in the core SDK itself. Deeper than > >> that, actually, it should be part of the model. > >> > >> - Robert > >> > >> On Fri, Nov 30, 2018 at 7:20 PM David Morávek <d...@apache.org> wrote: > >>> Jan, we made Kryo optional recently (it is a separate module and is used > >>> only in tests). From a quick look it seems that we forgot to remove > >>> compile time dependency from euphoria's build.gradle. Only "strong" > >>> dependencies I'm aware of are core SDK and guava. We'll be probably > >>> adding sketching extension dependency soon. > >>> > >>> D. > >>> > >>> On Fri, Nov 30, 2018 at 7:08 PM Jan Lukavský <je...@seznam.cz> wrote: > >>>> Hi Anton, > >>>> reactions inline. > >>>> > >>>> ---------- Původní e-mail ---------- > >>>> Od: Anton Kedin <ke...@google.com> > >>>> Komu: dev@beam.apache.org > >>>> Datum: 30. 11. 2018 18:17:06 > >>>> Předmět: Re: [DISCUSS] Structuring Java based DSLs > >>>> > >>>> I think this approach makes sense in general, Euphoria can be the > >>>> implementation detail of SQL, similar to Join Library or core SDK > >>>> Schemas. > >>>> > >>>> I wonder though whether it would be better to bring Euphoria closer to > >>>> core SDK first, maybe even merge them together. If you look at Reuven's > >>>> recent work around schemas it seems like there are already similarities > >>>> between that and Euphoria's approach, unless I'm missing the point (e.g. > >>>> Filter transforms, FullJoin vs CoGroup... see [2]). And we're already > >>>> switching parts of SQL to those transforms (e.g. SQL Aggregation is now > >>>> implemented by core SDK's Group[3]). > >>>> > >>>> > >>>> > >>>> Yes, these transforms seem to be very similar to those Euphoria has. > >>>> Whether or not to merge Euphoria with core is essentially just a > >>>> decision of the community (in my point of view). > >>>> > >>>> > >>>> > >>>> Adding explicit Schema support to Euphoria will bring it both closer to > >>>> core SDK and make it natural to use for SQL. Can this be a first step > >>>> towards this integration? > >>>> > >>>> > >>>> > >>>> Euphoria currently operates on pure PCollections, so when PCollection > >>>> has a schema, it will be accessible by Euphoria. It makes sense to make > >>>> use of the schema in Euphoria - it seems natural on inputs to Euphoria > >>>> operators, but it might be tricky (not saying impossible) to actually > >>>> produce schema-aware PCollections as outputs from Euphoria operators > >>>> (generally speaking, in special cases that might be possible). Regarding > >>>> inputs, there is actually intention to act on type of PCollection - e.g. > >>>> when PCollection is already of type KV, then it is possible to make key > >>>> extractor and value extractor optional in Euphoria builders, so it feels > >>>> natural to enable changing the builders when a schema-aware PCollection, > >>>> and make use of the provided schema. The rest of Euphoria team might > >>>> correct me, if I'm wrong. > >>>> > >>>> > >>>> > >>>> > >>>> One question I have is, does Euphoria bring dependencies that are not > >>>> needed by SQL, or does more or less only rely on the core SDK? > >>>> > >>>> > >>>> > >>>> I think the only relevant dependency that Euphoria has besides core SDK > >>>> is Kryo. It is the default coder when no coder is provided, but that > >>>> could be made optional - e.g. the default coder would be supported only > >>>> if an appropriate module would be available. That way I think that > >>>> Euphoria has no special dependencies. > >>>> > >>>> > >>>> > >>>> [1] > >>>> https://github.com/apache/beam/blob/f66eb5fe23b2500b396e6f711cdf4aeef6b31ab8/sdks/java/core/src/main/java/org/apache/beam/sdk/schemas/transforms/Group.java#L73 > >>>> [2] > >>>> https://github.com/apache/beam/tree/f66eb5fe23b2500b396e6f711cdf4aeef6b31ab8/sdks/java/core/src/main/java/org/apache/beam/sdk/schemas/transforms > >>>> [3] > >>>> https://github.com/apache/beam/blob/f66eb5fe23b2500b396e6f711cdf4aeef6b31ab8/sdks/java/extensions/sql/src/main/java/org/apache/beam/sdk/extensions/sql/impl/rel/BeamAggregationRel.java#L179 > >>>> > >>>> > >>>> > >>>> On Fri, Nov 30, 2018 at 6:29 AM Jan Lukavský <je...@seznam.cz> wrote: > >>>> > >>>> Hi community, > >>>> > >>>> I'm part of Euphoria DSL team, and on behalf of this team, I'd like to > >>>> discuss possible development of Java based DSLs currently present in > >>>> Beam. In my knowledge, there are currently two DSLs based on Java SDK - > >>>> Euphoria and SQL. These DSLs currently share only the SDK itself, > >>>> although there might be room to share some more effort. We already know > >>>> that both Euphoria and SQL have need for retractions, but there are > >>>> probably many more features that these two could share. > >>>> > >>>> So, I'd like to open a discussion on what it would cost and what it > >>>> would possibly bring, if instead of the current structure > >>>> > >>>> Java SDK > >>>> > >>>> | ---- SQL > >>>> > >>>> | ---- Euphoria > >>>> > >>>> these DSLs would be structured as > >>>> > >>>> Java SDK ---> Euphoria ---> SQL > >>>> > >>>> I'm absolutely sure that this would be a great investment and a huge > >>>> change, but I'd like to gather some opinions and general feelings of the > >>>> community about this. Some points to start the discussion from my side > >>>> would be, that structuring DSLs like this has internal logical > >>>> consistency, because each API layer further narrows completeness, but > >>>> brings simpler API for simpler tasks, while adding additional high-level > >>>> view of the data processing pipeline and thus enabling more > >>>> optimizations. On Euphoria side, these are various implementations joins > >>>> (most effective implementation depends on data), pipeline sampling and > >>>> more. Some (or maybe most) of these optimizations would have to be > >>>> implemented in both DSLs, so implementing them once is beneficial. > >>>> Another benefit is that this would bring Euphoria "closer" to Beam core > >>>> development (which would be good, it is part of the project anyway, > >>>> right? :)) and help better drive features, that although currently > >>>> needed mostly by SQL, might be needed by other Java users anyway. > >>>> > >>>> Thanks for discussion and looking forward to any opinions. > >>>> > >>>> Jan > >>>>
