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From "Jaeho Shin (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (GIRAPH-277) Text Vertex Input/Output Format base classes overhaul
Date Mon, 06 Aug 2012 21:41:02 GMT

     [ https://issues.apache.org/jira/browse/GIRAPH-277?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Jaeho Shin updated GIRAPH-277:
------------------------------

    Attachment: GIRAPH-277-2.patch

Ok, here's a new patch without the noises.

The correct reviewboard link: https://reviews.apache.org/r/6402/
(Jakob, sorry I couldn't update diff to the above, so created a new one)

In addition to minor fixes, there's a crucial one line change to the signature of {{TextVertexWriterToEachLine#writeVertex}}.
Using wildcard type here works fine when compiled together as source at the same time.  But
if I try to extend it from my own project depending on Giraph classes as jar, then I get strange
compilation error saying I'm not implementing {{writeVertex(Vertex<I, V, E, ?>)}} even
though it's already there on the superclass even marked final.  Removing the generics type
variables solves this problem so included the fix in this patch.  Maybe this is another thing
we should watch out when separating message types from I/O formats.
                
> 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-277-2.patch, 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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