To be honest, I don't think there's much worth doing right now. I
think more self-contained is better for Beam SQL, generally. Two
things I have on my mind are (1) SQL as an inline transform in every
SDK and (2) supporting pure SQL like the CLI and JDBC driver, where
the underlying language is an implementation detail.
Big picture / long term, I would envision pure SQL, embedded SQL
transform, and a DataFrame-like API in ~each SDK all desugaring to
relational algebra nodes, sharing an optimizer, sharing some amount of
mapping the physical plan to Beam transforms. The necessarily
SDK-specific parts are the embedded transform API and UDFs in the host
language. The rest should remain an implementation detail that we can
change.
- For example, it is easy to imagine a customized columnar
element/bundle encoding and SDK harness that only works for SQL to
remove overhead of being general purpose. It could be written in
C/C++/Go if we wanted to squeeze it for perf. Such things are made
harder by having an elaborate end-user API between SQL and the core
Beam model.
- Conversely, for whatever is chosen to underlie SQL's execution,
stability is paramount. Ideally the simplest and least likely to
change transforms would be the foundation. And I wouldn't want to have
to design a user-friendly API for Euphoria or the join library just to
enable a different join algorithm in SQL.
So my take is keep SQL flexible, implement SQL on low-level and stable
APIs, use join library, Euphoria, etc, if it looks like a big win, but
don't build any policy here or do big refactors right now.
Kenn
On Mon, Dec 3, 2018 at 9:31 AM Jan Lukavský <je...@seznam.cz
<mailto:je...@seznam.cz>> wrote:
Hi Robert,
currently there is no actual proposal, I was just trying to gather
feedback from the community. But my original thoughts would be [1]. I
actually don't see much need for restructuring the code by nesting
directories. If the community sees that it would make sense to
structure
the dependencies, the second step would probably be to figure out
how to
accomplish this. I don't have any exact solution in mind so far, it
would be probably needed to first identify features that are
needed by
SQL and not supported by Euphoria currently. Then we can actually
identify costs and see it this still makes sense.
Jan
On 12/3/18 6:17 PM, Robert Bradshaw wrote:
> 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
<mailto: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
<mailto: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 <mailto:ruw...@google.com>>
>>>> Komu: dev@beam.apache.org <mailto: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 <mailto: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 <mailto: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 <mailto:je...@seznam.cz>> wrote:
>>>>>> Hi Anton,
>>>>>> reactions inline.
>>>>>>
>>>>>> ---------- Původní e-mail ----------
>>>>>> Od: Anton Kedin <ke...@google.com <mailto:ke...@google.com>>
>>>>>> Komu: dev@beam.apache.org <mailto: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 <mailto: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
>>>>>>
