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From "Addison Phillips (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-550) Text constructure can throw exception
Date Fri, 22 Sep 2006 03:54:24 GMT
    [ http://issues.apache.org/jira/browse/HADOOP-550?page=comments#action_12436728 ] 
            
Addison Phillips commented on HADOOP-550:
-----------------------------------------

I had a hand in advising about this code (and wrote some of it). I agree with Doug Cutting
that the current implementation is rather too strict. The CodingErrorAction of REPLACE is
probably preferable as a default action.

One important difference between Text's implementation of UTF-8 and Java's String class: is:
Text validates for non-shortest form UTF-8, while String does not. Non-shortest form UTF-8
is sometimes exploited as a security flaw (and is NOT valid UTF-8, by rule) and the validate()
method inside Text prevents non-shortest sequences in Text objects.

I'd also note that non-UTF-8 data is pretty common, not usually because of unpaired surrogates,
but rather because of bad encoding identification or because of mixed UTF-8 and binary data.
Blowing chunks on that data is not a good choice as the default.

Providing for validation and tailorable reporting, a la NIO, actually would be the best course
of action. If the buffer isn't really UTF-8 and turns out to be an entirely different encoding
(probably the most common encoding problem), sometimes you might want to catch it as an exception,
but most often you'll probably be fine plunging ahead with U+FFFD (one per bad byte). For
the reason cited, I'd use the stricter Unicode rules for non-shortest UTF-8, but certainly
think that  just throwing an exception is too strict.



> Text constructure can throw exception
> -------------------------------------
>
>                 Key: HADOOP-550
>                 URL: http://issues.apache.org/jira/browse/HADOOP-550
>             Project: Hadoop
>          Issue Type: Bug
>            Reporter: Bryan Pendleton
>
> I finally got back around to moving my working code to using Text objects.
> And, once again, switching to Text (from UTF8) means my jobs are failing. This time,
its better defined - constructing a Text from a string extracted from Real World data makes
the Text object constructor throw a CharacterCodingException. This may be legit - I don't
actually understand UTF well enough to understand what's wrong with the supplied string. I'm
assembling a series of strings, some of which are user-supplied, and something causes the
Text constructor to barf.
> However, this is still completely unacceptable. If I need to stuff textual data someplace
- I need the container to *do* it. If user-supplied inputs can't be stored as a "UTF" aware
text value, then another container needs to be brought into existence. Sure, I can use a BytesWritable,
but, as its name implies - Text should handle "text". If Text is supposed to == "StringWritable",
then, well, it doesn't, yet.
> I admit to being a few weeks' back in the bleeding edge at this point, so maybe my particluar
Text bug has been fixed, though the only fixes to Text I see are adopting it into more of
the internals of Hadoop. This argument goes double in that case - if we're using Text objects
internally, it should really be a totally solid object - construct one from a String, get
one back, but _never_  throw a content-related Exception. Or, if Text is not the right object
because its data-sensitive, then I argue we shouldn't use it in any case where data might
kill it - internal, or anywhere else (by default).
> Please, don't remove UTF8, for now.

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