This patch adds support for unicode collation (searching and sorting).
Unicode collation is helpful in a search engine, for many languages you want things to match or sort differently.
You might even want to use copyfield and support different sort orders/matching schemes if you need to support multiple languages.
This is simply a factory for lucene's CollationKeyFilter, which indexes binary collation keys in a special format that preserves binary sort order.
I've added support for creating a Collator in two ways:
- system collator from a Locale spec (language + country + variant)
- tailored collator from custom rules in a text file
in no way is there an option to use the "default" locale of the jvm, (I consider this a bit dangerous)
in this patch, it is mandatory to define the locale explicitly for a system collator.
The required lucene-collation-2.9.1.jar is only 12KB.