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https://issues.apache.org/jira/browse/GIRAPH-277?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13427697#comment-13427697
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Eli Reisman commented on GIRAPH-277:
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That was a lot of work, good job. This does need to be made easier, I agree. As
far as the preprocessing, it seems a bit over engineered as it just pushes the
parsing work to another thing the user has to implement, and they still have to
place those values, so the net difficulty does not really change for the IO
format author. Adding more generics to this already loaded-up area of the code
does not seem to welcome in the new users either.
The new thinking on IO formats as it was explained to me is that developers
should be providing lots of IO formats, and that users should simply specify an
appropriate one at the command line with -if -of. The benchmark code is the
"old way", the examples/ code is more representative of what I was told we want
now, which is you specify IO at the command line, write your vertex class, and
you're done. So if the IO code seems a bit cryptic the way it is (I agree!) its
also not meant to be user-facing anymore, at least not for new users. This also
means a really useful upgrade (some are in the works now) would be to add
support for more IO formats (Avro etc.) and more strongly typed subclasses for
the ones we have, thereby presenting the user with lots of reasons not to write
their own IO formats at all. This "new thinking" has also not been properly
documented on the site/wiki.
That said, great work and as long as the record reader plumbing coming out of
Hadoop is properly tested and still happy in these IO formats (have you run
jobs with this patch and real chunk of sample data or just unit tests on mvn?)
then this looks great. I'd be happier without the custom exception and
preprocessing stuff, but if others find this useful then good enough for me.
> Text Vertex Input/Output Format base classes overhaul
> -----------------------------------------------------
>
> Key: GIRAPH-277
> URL: https://issues.apache.org/jira/browse/GIRAPH-277
> Project: Giraph
> Issue Type: Improvement
> Components: examples, lib
> Reporter: Jaeho Shin
> Attachments: GIRAPH-277.patch
>
>
> The current way of implementing {{VertexInputFormat}} and {{VertexReader}}
> had bad smell. It required users to understand how these two classes are
> glued together, and forced similar codes to be duplicated in every new input
> format. (Similarly for the VertexOutputFormat and VertexWriter.) Anyone who
> wants to create a new format should create an underlying record reader or
> writer at the right moment and delegate some calls to it, which seemed
> unnecessary detail being exposed. Besides, type parameters had to appear all
> over every new format code, which was extremely annoying for both reading
> existing code and writing a new one. I was very frustrated writing my first
> format code especially when I compared it to writing a new vertex code. I
> thought writing a new input/output format should be as simple as vertex.
> So, I have refactored {{TextVertexInputFormat}} and {{OutputFormat}} into new
> forms that have no difference in their interfaces, but remove a lot of burden
> for subclassing. Instead of providing static VertexReader base classes, I
> made it a non-static inner-class of its format class, which helps eliminate
> the repeated code for gluing these two, already tightly coupled classes.
> This has additional advantage of eliminating all the Generics type variables
> on the VertexReader side, which makes overall code much more concise. I
> added several useful TextVertexReader base classes that can save efforts for
> implementing line-oriented formats.
> Please comment if you see my proposed change have any impact on other
> aspects. I'm unsure of how these additional layers of abstraction could
> affect performance.
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