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https://issues.apache.org/jira/browse/LUCENE-9100?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17010934#comment-17010934
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Elbek Kamoliddinov commented on LUCENE-9100:
--------------------------------------------
I made some progress on this, I found a case where following text influences
whatever text it follows, For example this text {{日本語【単話版】}} produces following
tokens:
{code:java}
日本
日本語
語
単
話
版
{code}
But with this text {{日本語 単話版}}
{code:java}
日本語
単
話
版 {code}
This char {{【}} influences how first 3 chars are tokenized, but the char itself
is punctuation char. Wouldn't it make sense to treat punctuation chars as a
token breaker and cut its influence?
The code I used to produce the tokens:
{code:java}
Analyzer analyzer = new Analyzer() {
@Override
protected TokenStreamComponents createComponents(String fieldName) {
Tokenizer tokenizer = new
JapaneseTokenizer(newAttributeFactory(), null, true,
JapaneseTokenizer.Mode.SEARCH);
return new TokenStreamComponents(tokenizer, new
LowerCaseFilter(tokenizer));
}
};
try (TokenStream tokens = analyzer.tokenStream("field", new
StringReader("日本語 単話版"))) {
CharTermAttribute chars =
tokens.addAttribute(CharTermAttribute.class);
tokens.reset();
while (tokens.incrementToken()) {
System.out.println(chars.toString());
}
tokens.end();
} catch (IOException e) {
// should never happen with a StringReader
throw new RuntimeException(e);
}
{code}
> JapaneseTokenizer produces inconsistent tokens
> ----------------------------------------------
>
> Key: LUCENE-9100
> URL: https://issues.apache.org/jira/browse/LUCENE-9100
> Project: Lucene - Core
> Issue Type: Bug
> Components: modules/analysis
> Affects Versions: 7.2
> Reporter: Elbek Kamoliddinov
> Priority: Major
>
> We use {{JapaneseTokenizer}} on prod and seeing some inconsistent behavior.
> With this text:
> {{"マギアリス【単版話】 4話 (Unlimited Comics)"}} I get different results if I insert
> space before `【` char. Here is the small code snippet demonstrating the case
> (note we use our own dictionary and connection costs):
> {code:java}
> Analyzer analyzer = new Analyzer() {
> @Override
> protected TokenStreamComponents createComponents(String
> fieldName) {
> // Tokenizer tokenizer = new
> JapaneseTokenizer(newAttributeFactory(), null, true,
> JapaneseTokenizer.Mode.SEARCH);
> Tokenizer tokenizer = new
> JapaneseTokenizer(newAttributeFactory(), dictionaries.systemDictionary,
> dictionaries.unknownDictionary, dictionaries.connectionCosts, null, true,
> JapaneseTokenizer.Mode.SEARCH);
> return new TokenStreamComponents(tokenizer, new
> LowerCaseFilter(tokenizer));
> }
> };
> String text1 = "マギアリス【単版話】 4話 (Unlimited Comics)";
> String text2 = "マギアリス 【単版話】 4話 (Unlimited Comics)"; //inserted space
> try (TokenStream tokens = analyzer.tokenStream("field", new
> StringReader(text1))) {
> CharTermAttribute chars =
> tokens.addAttribute(CharTermAttribute.class);
> tokens.reset();
> while (tokens.incrementToken()) {
> System.out.println(chars.toString());
> }
> tokens.end();
> } catch (IOException e) {
> // should never happen with a StringReader
> throw new RuntimeException(e);
> } {code}
> Output is:
> {code:java}
> //text1
> マギ
> アリス
> 単
> 版
> 話
> 4
> 話
> unlimited
> comics
> //text2
> マギア
> リス
> 単
> 版
> 話
> 4
> 話
> unlimited
> comics{code}
> It looks like tokenizer doesn't view the punctuation ({{【}} is
> {{Character.START_PUNCTUATION}} type) as an indicator that there should be a
> token break, and somehow 【 punctuation char causes difference in the output.
> If I use the {{JapaneseTokenizer}} tokenizer then this problem doesn't
> manifest because it doesn't tokenize {{マギアリス}} into multiple tokens and
> outputs as is.
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