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From "Michael McCandless (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-1906) Problem with CharStream and Tokenizers with custom reset(Reader) method
Date Thu, 10 Sep 2009 17:39:57 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-1906?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12753720#action_12753720
] 

Michael McCandless commented on LUCENE-1906:
--------------------------------------------

bq. We also have a not-in-CHANGES.txt backwards break.

Sigh, I forgot to also add an entry to "Changes in back compat policy"
when we made this change (in LUCENE-1466).

We had decided at the time to make an exception to back-compat, ie
allow reader to become CharStream, but we can definitely revisit
that...

bq. One possibility to prevent this break would be the following

Adding an instanceof check in every correctOffset call makes me
nervous -- what's the performance cost?


> Problem with CharStream and Tokenizers with custom reset(Reader) method
> -----------------------------------------------------------------------
>
>                 Key: LUCENE-1906
>                 URL: https://issues.apache.org/jira/browse/LUCENE-1906
>             Project: Lucene - Java
>          Issue Type: Bug
>          Components: Analysis
>    Affects Versions: 2.9
>            Reporter: Uwe Schindler
>            Assignee: Uwe Schindler
>            Priority: Blocker
>             Fix For: 2.9
>
>         Attachments: backwards-break.patch, LUCENE-1906.patch
>
>
> When reviewing the new CharStream code added to Tokenizers, I found a
> serious problem with backwards compatibility and other Tokenizers, that do
> not override reset(CharStream).
> The problem is, that e.g. CharTokenizer only overrides reset(Reader):
> {code}
>   public void reset(Reader input) throws IOException {
>     super.reset(input);
>     bufferIndex = 0;
>     offset = 0;
>     dataLen = 0;
>   }
> {code}
> If you reset such a Tokenizer with another CharStream (not a Reader), this
> method will never be called and breaking the whole Tokenizer.
> As CharStream extends Reader, I propose to remove this reset(CharStream
> method) and simply do an instanceof check to detect if the supplied Reader
> is no CharStream and wrap it. We could also remove the extra ctor (because
> most Tokenizers have no support for passing CharStreams). If the ctor also
> checks with instanceof and warps as needed the code is backwards compatible
> and we do not need to add additional ctors in subclasses.
> As this instanceof check is always done in CharReader.get() why not remove
> ctor(CharStream) and reset(CharStream) completely?
> Any thoughts?
> I would like to fix this somehow before RC4, I'm, sorry :(

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