[LUCENE-2784] Change all FilteredTermsEnum impls into TermsEnum decorators

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 4.0-ALPHA
• Lucene Fields: New, Patch Available
• Assignee: Uwe Schindler
• Reporter: Robert Muir
• Created: 29/Nov/10 16:39
• Updated: 28/Aug/22 12:36
• Resolved: 30/Nov/10 01:23

Description

Currently, FilteredTermsEnum has two ctors:

• FilteredTermsEnum(IndexReader reader, String field)
• FilteredTermsEnum(TermsEnum tenum)

But most of our concrete implementations (e.g. TermsRangeEnum) use the IndexReader+field ctor

In my opinion we should remove this ctor, and switch over all FilteredTermsEnum implementations to just take a TermsEnum.

Advantages:

• This simplifies FilteredTermsEnum and its subclasses, where they are more decorator-like (perhaps in the future we could compose them)
• Removes silly checks such as if (tenum == null) in every next()
• Allows for consumers to pass in enumerators however they want: e.g. its their responsibility if they want to use MultiFields or not, it shouldnt be buried in FilteredTermsEnum.

I created a quick patch (all core+contrib+solr tests pass), but i think this opens up more possibilities for refactoring improvements that haven't yet been done in the patch: we should explore these too.