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From "Steven Rowe (JIRA)" <>
Subject [jira] Commented: (LUCENE-2019) map unicode process-internal codepoints to replacement character
Date Sat, 31 Oct 2009 02:32:59 GMT


Steven Rowe commented on LUCENE-2019:

Steven, by the way, I think something i havent been able to communicate properly, is that
I feel very strongly that storing noncharacters in term text where they are treated as abstract
characters, is very different than using them as sentinel values / delimiters / etc in the
index format, I think this is ok and is what they are for.

but term text is different, search engines index human language and by putting noncharacters
in term text you are treating them as abstract characters.

Robert, you are a proponent of the (ICU)CollationKeyFilter functionality, which uses IndexableBinaryStringTools
to store arbitrary binary data in a Lucene index.  These filters store non-human-readable
terms in the index.  I can think of several other examples of using Lucene indexes to store
non-human-language terms.

Character data, in addition to representing characters, is *data*.  Bits.  I would argue that
you *always* need context to figure out what bits represent.

> map unicode process-internal codepoints to replacement character
> ----------------------------------------------------------------
>                 Key: LUCENE-2019
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Index
>            Reporter: Robert Muir
>            Priority: Minor
>         Attachments: LUCENE-2019.patch
> A spinoff from LUCENE-2016.
> There are several process-internal codepoints in unicode, we should not store these in
the index.
> Instead they should be mapped to replacement character (U+FFFD), so they can be used
> An example of this is how Lucene Java currently uses U+FFFF process-internally, it can't
be in the index or will cause problems. 

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