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From "Shad Storhaug (JIRA)" <j...@apache.org>
Subject [jira] [Created] (LUCENENET-612) SERIOUS issues with PerFieldAnalyzerWrapper in 4.8
Date Mon, 12 Aug 2019 00:26:00 GMT
Shad Storhaug created LUCENENET-612:
---------------------------------------

             Summary: SERIOUS issues with PerFieldAnalyzerWrapper in 4.8
                 Key: LUCENENET-612
                 URL: https://issues.apache.org/jira/browse/LUCENENET-612
             Project: Lucene.Net
          Issue Type: Bug
          Components: Lucene.Net.Analysis.Common
    Affects Versions: Lucene.Net 4.8.0
            Reporter: Shad Storhaug


This came in on the user mailing list on 15-July-2019 and was originally reported by Bryan
Rojo (BryanRojo@elliotelectric.com)

 
{quote}Not necessarily a bug, but for some people who use PerFieldAnalyzerWrapper like I do
this might be worth noting.

PerFieldAnalyzerWrapper has been "improved" in 4.8 and now uses a PER_FIELD_REUSE_STRATEGY
which means that the tokenized fields will be stored in a dictionary, so If you have multiple
fields with the same name in your document, then you will only be able to index the very first
one that makes it into that dictionary.

So the problem with this is that you can potentially lose thousands of terms in your index,
which could cause your searches to be of very low quality.

BEWARE.
{quote}
 
There are 2 issues that need to be resolved to address this:

1. The documentation for {{PerFieldAnalyzerWrapper}} should be updated to inform users that
if they need to use multiple dictionary keys, they should use {{TreeDictionary<K, V>}}.
2. {{TreeDictionary<K, V>}} does not currently implement {{System.Collections.Generic.IDictionary<TKey,
TValue>}}, as it was brought over from C5 as-is.

Another thing of note is that C5 has added support for .NET Standard 1.0 since this was brought
over.

However, there still seems to be a few problems that make the C5 types incompatible with Lucene.Net,
most notably the lack of support for {{System.Collections.Generic.IDictionary<TKey, TValue>}}
in {{TreeDictionary}} and {{System.Collections.Generic.ISet<T>}} in {{TreeSet}} (the
latter of which has already been patched in {{Lucene.Net.Support.TreeSet}}).

I [reported|https://github.com/sestoft/C5/issues/53] the lack of support for {{ISet<T>}}
on 6-Nov-2016, but although the maintainers agree this should be done, it still hasn't been.
Perhaps a PR to the C5 project is the way to get this done, which would allow us to finally
remove these collection copies from Lucene.Net.Support and add a package dependency on C5.

Another option is to shop around to see if there are any other generic TreeSet/TreeDictionary
implementations that have popped up since late 2016 that we can check for compatibility.



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