Mailing-List: contact dev-help@flink.apache.org; run by ezmlm
Precedence: bulk
Reply-To: dev@flink.apache.org
Message-ID: <55BEA133.1090402@informatik.hu-berlin.de>
Date: Mon, 03 Aug 2015 01:01:07 +0200
From: "Matthias J. Sax" <mjsax@informatik.hu-berlin.de>
User-Agent: Mozilla/5.0 (X11; Linux x86_64;
 rv:31.0) Gecko/20100101 Icedove/31.7.0
MIME-Version: 1.0
To: dev@flink.apache.org
Subject: Re: Tuple
References: <55BBCE60.2060305@informatik.hu-berlin.de>
	<55BBDD2B.9060703@fu-berlin.de>	<55BBDE43.2030608@fu-berlin.de>
	<55BCA7CE.7000603@informatik.hu-berlin.de>
	<55BCAFC5.3080102@informatik.hu-berlin.de>
	<CANC1h_usm59ge_s3JOUug9LsT_1OzQKM8pdY+41LB8Ysxou6dw@mail.gmail.com>
	<55BE6E65.3000903@informatik.hu-berlin.de>	<55BE980B.9000003@fu-berlin.de>
	<55BE9D6D.5040709@informatik.hu-berlin.de>
 <CANC1h_sD0=sbN+eM_Bi4ga1Vz=b-MHvZYnChLpFvRdbvS5_Lww@mail.gmail.com>
In-Reply-To: 
 <CANC1h_sD0=sbN+eM_Bi4ga1Vz=b-MHvZYnChLpFvRdbvS5_Lww@mail.gmail.com>
Content-Type: multipart/signed; micalg=pgp-sha256;
 protocol="application/pgp-signature";
 boundary="HCD41tjO70kurBIQaC7EIsmMIEWJQkW6b"

--HCD41tjO70kurBIQaC7EIsmMIEWJQkW6b
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable

Thanks for the advice about Tuple0.

I personally don't see any advantage in having "flink-tuple" project. Do
I miss anything about it? Furthermore, I am not sure if it is a good
idea the have too many too small projects.


On 08/03/2015 12:48 AM, Stephan Ewen wrote:
> Tuple0 would need special serialization and comparator logic. If that i=
s
> given, I see no reason not to support it.
>=20
> There is BTW, the request to create a dedicated "flink-tuple" project, =
that
> only contains the tuple classes. Any opinions on that?
>=20
> On Mon, Aug 3, 2015 at 12:45 AM, Matthias J. Sax <
> mjsax@informatik.hu-berlin.de> wrote:
>=20
>> Thanks for the explanation!
>>
>> As I mentioned before, Tuple0 might also be helpful for streaming. And=
 I
>> guess I will need it for Storm compatibility layer, too. (I need to
>> double check, but Storm supports zero-attribute-tuples, too).
>>
>> With regard to the information I collected during the discussion, I vo=
te
>> for keeping Tuple0 in Flink core, and fix the serialization problem.
>> Should we have another JIRA for this? Or should I extend the existing
>> JIRA? (https://issues.apache.org/jira/browse/FLINK-2457)
>>
>> -Matthias
>>
>>
>> On 08/03/2015 12:22 AM, Chesnay Schepler wrote:
>>> First of all, it was a really good idea to start a discussion about t=
his.
>>>
>>> So the general idea behind Tuple0 was this:
>>>
>>> The Python API maps python tuples to flink tuples. Python can have em=
pty
>>> tuples, so i thought "well duh, let's make a Tuple0 class!". What i d=
id
>>> not wanna do is create some non-Tuple object to represent empty tuple=
s,
>>> I'd rather have them treated the same, because it's less work and
>>> creates simpler code.
>>>
>>> When transferring the plan to java, certain parameters for operations=

>>> are tuples, which can be empty aswell.
>>> This is where the Tuple0 class is really useful, because these empty
>>> tuples go through the same logic as other tuples.
>>> This is also why i want to keep the class, at least in the python
>>> project, for now.
>>>
>>> For the actual program execution, I need a new solution. Funny story,=

>>> while writing this reply i noticed that the Python API can't handle
>>> Tuple0 at runtime aswell. ha...ha... -.-
>>>
>>> Guess I now know what I'm working on next.
>>>
>>> On 02.08.2015 21:24, Matthias J. Sax wrote:
>>>> Can you elaborate how and why Python used Tuple0? If it cannot be
>>>> serialized similar to regular Tuples, what is the usage in Python? R=
ight
>>>> now it seems, as there is no special serialization code for Tuple0.
>>>>
>>>> I just want to understand the topic in detail.
>>>>
>>>> -Matthias
>>>>
>>>>
>>>> On 08/01/2015 03:38 PM, Stephan Ewen wrote:
>>>>> I think a Tuple0 cannot be implemented like the current tuples, at
>> least
>>>>> with respect to runtime serialization.
>>>>>
>>>>> The system makes the assumption that it makes progress in consuming=

>>>>> bytes
>>>>> when deserializing values. If a Tuple=3D never consumes data from t=
he
>> byte
>>>>> stream, this assumption is broken. It would need at least one marke=
r
>>>>> byte.
>>>>> Then it effectively is a Tuple1<Byte> disgusing itself as a tuple0.=

>>>>>
>>>>>
>>>>>
>>>>> On Sat, Aug 1, 2015 at 1:38 PM, Matthias J. Sax <
>>>>> mjsax@informatik.hu-berlin.de> wrote:
>>>>>
>>>>>> I just double checked. Scala does not have type Tuple0. IMHO, it w=
ould
>>>>>> be best to remove Tuple0 for consistency. Having Tuple types is fo=
r
>>>>>> consistency reason with Scala in the first place, right? Please gi=
ve
>>>>>> feedback.
>>>>>>
>>>>>> -Matthias
>>>>>>
>>>>>>
>>>>>> On 08/01/2015 01:04 PM, Matthias J. Sax wrote:
>>>>>>> I see.
>>>>>>>
>>>>>>> I think that it might be useful to have Tuple0, because in rare
>> cases,
>>>>>>> you only want to "notify" a downstream operators (taking about
>>>>>>> streaming) that something happened but there is no actual data to=
 be
>>>>>>> processed. Furthermore, if Flink cannot deal with Tuple0 it shoul=
d be
>>>>>>> removed completely for consistency IMHO.
>>>>>>>
>>>>>>> I will open a JIRA for it.
>>>>>>>
>>>>>>> -Matthias
>>>>>>>
>>>>>>> On 07/31/2015 10:44 PM, Chesnay Schepler wrote:
>>>>>>>> also, I'm not sure if I ever sent a Tuple0 through a program, it=

>>>>>>>> could
>>>>>>>> be that the system freaks out.
>>>>>>>>
>>>>>>>> On 31.07.2015 22:40, Chesnay Schepler wrote:
>>>>>>>>> there's no specific reason. it was added fairly recently by me
>>>>>>>>> (mid of
>>>>>>>>> april), and you're most likely the second person to use it.
>>>>>>>>>
>>>>>>>>> i didn't integrate into all our tuple related stuff because, we=
ll,
>> i
>>>>>>>>> never thought anyone would actually need it, so i saved myself =
the
>>>>>>>>> trouble.
>>>>>>>>>
>>>>>>>>>> Hi,
>>>>>>>>>>
>>>>>>>>>> is there any specific reason, why Tuple.getTupleClass(int arit=
y)
>>>>>>>>>> does
>>>>>>>>>> not support arity zero? There is a class Tuple0, but it cannot=
 be
>>>>>>>>>> generator by Tuple.getTupleClass(...). Is it a missing feature=
 (I
>>>>>> would
>>>>>>>>>> like to have it).
>>>>>>>>>>
>>>>>>>>>> -Matthias
>>>>>>>>>>
>>>>>>>>>
>>>>>>
>>>
>>
>>
>=20


--HCD41tjO70kurBIQaC7EIsmMIEWJQkW6b
Content-Type: application/pgp-signature; name="signature.asc"
Content-Description: OpenPGP digital signature
Content-Disposition: attachment; filename="signature.asc"

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2
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=XSJ5
-----END PGP SIGNATURE-----

--HCD41tjO70kurBIQaC7EIsmMIEWJQkW6b--