Robert, I filed https://issues.apache.org/jira/browse/BEAM-7015 for removing the Python SDK copy of standard_coders.yaml and assigned it to you.
On Fri, Apr 5, 2019 at 9:24 AM Kenneth Knowles <k...@apache.org> wrote: > Nested and unnested contexts are two different encodings. Can we just give > them different URNs? We can even just express the length-prefixed UTF-8 as > a composition of the length-prefix URN and the UTF-8 URN. > > On Fri, Apr 5, 2019 at 12:38 AM Robert Bradshaw <rober...@google.com> > wrote: > >> On Fri, Apr 5, 2019 at 12:50 AM Heejong Lee <heej...@google.com> wrote: >> > >> > Robert, does nested/unnested context work properly for Java? >> >> I believe so. It is similar to the bytes coder, that prefixes vs. not >> based on the context. >> >> > I can see that the Context is fixed to NESTED[1] and the encode method >> with the Context parameter is marked as deprecated[2]. >> > >> > [1]: >> https://github.com/apache/beam/blob/0868e7544fd1e96db67ff5b9e70a67802c0f0c8e/sdks/java/core/src/main/java/org/apache/beam/sdk/coders/StringUtf8Coder.java#L68 >> > [2]: >> https://github.com/apache/beam/blob/0868e7544fd1e96db67ff5b9e70a67802c0f0c8e/sdks/java/core/src/main/java/org/apache/beam/sdk/coders/Coder.java#L132 >> >> That doesn't mean it's unused, e.g. >> >> >> https://github.com/apache/beam/blob/release-2.12.0/sdks/java/core/src/main/java/org/apache/beam/sdk/util/CoderUtils.java#L160 >> >> https://github.com/apache/beam/blob/release-2.12.0/sdks/java/core/src/main/java/org/apache/beam/sdk/coders/LengthPrefixCoder.java#L64 >> >> (and I'm sure there's others). >> >> > On Thu, Apr 4, 2019 at 3:25 PM Robert Bradshaw <rober...@google.com> >> wrote: >> >> >> >> I don't know why there are two separate copies of >> >> standard_coders.yaml--originally there was just one (though it did >> >> live in the Python directory). I'm guessing a copy was made rather >> >> than just pointing both to the new location, but that completely >> >> defeats the point. I can't seem to access JIRA right now; could >> >> someone file an issue to resolve this? >> >> >> >> I also think the spec should be next to the definition of the URN, >> >> that's one of the reason the URNs were originally in a markdown file >> >> (to encourage good documentation, literate programming style). Many >> >> coders already have their specs there. >> >> >> >> Regarding backwards compatibility, we can't change existing coders, >> >> and making new coders won't help with inference ('cause changing that >> >> would also be backwards incompatible). Fortunately, I think we're >> >> already doing the consistent thing here: In both Python and Java the >> >> raw UTF-8 encoded bytes are encoded when used in an *unnested* context >> >> and the length-prefixed UTF-8 encoded bytes are used when the coder is >> >> used in a *nested* context. >> >> >> >> I'd really like to see the whole nested/unnested context go away, but >> >> that'll probably require Beam 3.0; it causes way more confusion than >> >> the couple of bytes it saves in a couple of places. >> >> >> >> - Robert >> >> >> >> On Thu, Apr 4, 2019 at 10:55 PM Robert Burke <rob...@frantil.com> >> wrote: >> >> > >> >> > My 2cents is that the "Textual description" should be part of the >> documentation of the URNs on the Proto messages, since that's the common >> place. I've added a short description for the varints for example, and we >> already have lenghthier format & protocol descriptions there for iterables >> and similar. >> >> > >> >> > The proto [1] *can be* the spec if we want it to be. >> >> > >> >> > [1]: >> https://github.com/apache/beam/blob/069fc3de95bd96f34c363308ad9ba988ab58502d/model/pipeline/src/main/proto/beam_runner_api.proto#L557 >> >> > >> >> > On Thu, 4 Apr 2019 at 13:51, Kenneth Knowles <k...@apache.org> >> wrote: >> >> >> >> >> >> >> >> >> >> >> >> On Thu, Apr 4, 2019 at 1:49 PM Robert Burke <rob...@frantil.com> >> wrote: >> >> >>> >> >> >>> We should probably move the "java" version of the yaml file [1] to >> a common location rather than deep in the java hierarchy, or copying it for >> Go and Python, but that can be a separate task. It's probably non-trivial >> since it looks like it's part of a java resources structure. >> >> >> >> >> >> >> >> >> Seems like /model is a good place for this if we don't want to >> invent a new language-independent hierarchy. >> >> >> >> >> >> Kenn >> >> >> >> >> >> >> >> >>> >> >> >>> Luke, the Go SDK doesn't currently do this validation, but it >> shouldn't be difficult, given pointers to the Java and Python variants of >> the tests to crib from [2]. Care would need to be taken so that Beam Go SDK >> users (such as they are) aren't forced to run them, and not have the yaml >> file to read. I'd suggest putting it with the integration tests [3]. >> >> >>> >> >> >>> I've filed a JIRA (BEAM-7009) for tracking this Go SDK side work. >> [4] >> >> >>> >> >> >>> 1: >> https://github.com/apache/beam/blob/master/model/fn-execution/src/main/resources/org/apache/beam/model/fnexecution/v1/standard_coders.yaml >> >> >>> 2: >> https://github.com/apache/beam/search?q=standard_coders.yaml&unscoped_q=standard_coders.yaml >> >> >>> 3: https://github.com/apache/beam/tree/master/sdks/go/test >> >> >>> 4: https://issues.apache.org/jira/browse/BEAM-7009 >> >> >>> >> >> >>> >> >> >>> On Thu, 4 Apr 2019 at 13:28, Lukasz Cwik <lc...@google.com> wrote: >> >> >>>> >> >> >>>> >> >> >>>> >> >> >>>> On Thu, Apr 4, 2019 at 1:15 PM Chamikara Jayalath < >> chamik...@google.com> wrote: >> >> >>>>> >> >> >>>>> >> >> >>>>> >> >> >>>>> On Thu, Apr 4, 2019 at 12:15 PM Lukasz Cwik <lc...@google.com> >> wrote: >> >> >>>>>> >> >> >>>>>> standard_coders.yaml[1] is where we are currently defining >> these formats. >> >> >>>>>> Unfortunately the Python SDK has its own copy[2]. >> >> >>>>> >> >> >>>>> >> >> >>>>> Ah great. Thanks for the pointer. Any idea why there's a >> separate copy for Python ? I didn't see a significant difference in >> definitions looking at few random coders there but I might have missed >> something. If there's no reason to maintain two, we should probably unify. >> >> >>>>> Also, seems like we haven't added the definition for UTF-8 coder >> yet. >> >> >>>>> >> >> >>>> >> >> >>>> Not certain as well. I did notice the timer coder definition >> didn't exist in the Python copy. >> >> >>>> >> >> >>>>>> >> >> >>>>>> >> >> >>>>>> Here is an example PR[3] that adds the "beam:coder:double:v1" >> as tests to the Java and Python SDKs to ensure interoperability. >> >> >>>>>> >> >> >>>>>> Robert Burke, does the Go SDK have a test where it uses >> standard_coders.yaml and runs compatibility tests? >> >> >>>>>> >> >> >>>>>> Chamikara, creating new coder classes is a pain since the type >> -> coder mapping per SDK language would select the non-well known type if >> we added a new one to a language. If we swapped the default type->coder >> mapping, this would still break update for pipelines forcing users to >> update their code to select the non-well known type. If we don't change the >> default type->coder mapping, the well known coder will gain little usage. I >> think we should fix the Python coder to use the same encoding as Java for >> UTF-8 strings before there are too many Python SDK users. >> >> >>>>> >> >> >>>>> >> >> >>>>> I was thinking that may be we should just change the default >> UTF-8 coder for Fn API path which is experimental. Updating Python to do >> what's done for Java is fine if we agree that encoding used for Java should >> be the standard. >> >> >>>>> >> >> >>>> >> >> >>>> That is a good idea to use the Fn API experiment to control which >> gets selected. >> >> >>>> >> >> >>>>>> >> >> >>>>>> >> >> >>>>>> 1: >> https://github.com/apache/beam/blob/master/model/fn-execution/src/main/resources/org/apache/beam/model/fnexecution/v1/standard_coders.yaml >> >> >>>>>> 2: >> https://github.com/apache/beam/blob/master/sdks/python/apache_beam/testing/data/standard_coders.yaml >> >> >>>>>> 3: https://github.com/apache/beam/pull/8205 >> >> >>>>>> >> >> >>>>>> On Thu, Apr 4, 2019 at 11:50 AM Chamikara Jayalath < >> chamik...@google.com> wrote: >> >> >>>>>>> >> >> >>>>>>> >> >> >>>>>>> >> >> >>>>>>> On Thu, Apr 4, 2019 at 11:29 AM Robert Bradshaw < >> rober...@google.com> wrote: >> >> >>>>>>>> >> >> >>>>>>>> A URN defines the encoding. >> >> >>>>>>>> >> >> >>>>>>>> There are (unfortunately) *two* encodings defined for a Coder >> (defined >> >> >>>>>>>> by a URN), the nested and the unnested one. IIRC, in both >> Java and >> >> >>>>>>>> Python, the nested one prefixes with a var-int length, and the >> >> >>>>>>>> unnested one does not. >> >> >>>>>>> >> >> >>>>>>> >> >> >>>>>>> Could you clarify where we define the exact encoding ? I only >> see a URN for UTF-8 [1] while if you look at the implementations Java >> includes length in the encoding [1] while Python [1] does not. >> >> >>>>>>> >> >> >>>>>>> [1] >> https://github.com/apache/beam/blob/069fc3de95bd96f34c363308ad9ba988ab58502d/model/pipeline/src/main/proto/beam_runner_api.proto#L563 >> >> >>>>>>> [2] >> https://github.com/apache/beam/blob/master/sdks/java/core/src/main/java/org/apache/beam/sdk/coders/StringUtf8Coder.java#L50 >> >> >>>>>>> [3] >> https://github.com/apache/beam/blob/master/sdks/python/apache_beam/coders/coders.py#L321 >> >> >>>>>>> >> >> >>>>>>> >> >> >>>>>>>> >> >> >>>>>>>> >> >> >>>>>>>> We should define the spec clearly and have cross-language >> tests. >> >> >>>>>>> >> >> >>>>>>> >> >> >>>>>>> +1 >> >> >>>>>>> >> >> >>>>>>> Regarding backwards compatibility, I agree that we should >> probably not update existing coder classes. Probably we should just >> standardize the correct encoding (may be as a comment near corresponding >> URN in the beam_runner_api.proto ?) and create new coder classes as needed. >> >> >>>>>>> >> >> >>>>>>>> >> >> >>>>>>>> >> >> >>>>>>>> On Thu, Apr 4, 2019 at 8:13 PM Pablo Estrada < >> pabl...@google.com> wrote: >> >> >>>>>>>> > >> >> >>>>>>>> > Could this be a backwards-incompatible change that would >> break pipelines from upgrading? If they have data in-flight in between >> operators, and we change the coder, they would break? >> >> >>>>>>>> > I know very little about coders, but since nobody has >> mentioned it, I wanted to make sure we have it in mind. >> >> >>>>>>>> > -P. >> >> >>>>>>>> > >> >> >>>>>>>> > On Wed, Apr 3, 2019 at 8:33 PM Kenneth Knowles < >> k...@apache.org> wrote: >> >> >>>>>>>> >> >> >> >>>>>>>> >> Agree that a coder URN defines the encoding. I see that >> string UTF-8 was added to the proto enum, but it needs a written spec of >> the encoding. Ideally some test data that different languages can use to >> drive compliance testing. >> >> >>>>>>>> >> >> >> >>>>>>>> >> Kenn >> >> >>>>>>>> >> >> >> >>>>>>>> >> On Wed, Apr 3, 2019 at 6:21 PM Robert Burke < >> rob...@frantil.com> wrote: >> >> >>>>>>>> >>> >> >> >>>>>>>> >>> String UTF8 was recently added as a "standard coder " URN >> in the protos, but I don't think that developed beyond Java, so adding it >> to Python would be reasonable in my opinion. >> >> >>>>>>>> >>> >> >> >>>>>>>> >>> The Go SDK handles Strings as "custom coders" presently >> which for Go are always length prefixed (and reported to the Runner as >> LP+CustomCoder). It would be straight forward to add the correct handling >> for strings, as Go natively treats strings as UTF8. >> >> >>>>>>>> >>> >> >> >>>>>>>> >>> >> >> >>>>>>>> >>> On Wed, Apr 3, 2019, 5:03 PM Heejong Lee < >> heej...@google.com> wrote: >> >> >>>>>>>> >>>> >> >> >>>>>>>> >>>> Hi all, >> >> >>>>>>>> >>>> >> >> >>>>>>>> >>>> It looks like UTF-8 String Coder in Java and Python SDKs >> uses different encoding schemes. StringUtf8Coder in Java SDK puts the >> varint length of the input string before actual data bytes however >> StrUtf8Coder in Python SDK directly encodes the input string to bytes >> value. For the last few weeks, I've been testing and fixing cross-language >> IO transforms and this discrepancy is a major blocker for me. IMO, we >> should unify the encoding schemes of UTF8 strings across the different SDKs >> and make it a standard coder. Any thoughts? >> >> >>>>>>>> >>>> >> >> >>>>>>>> >>>> Thanks, >> >
