[LUCENE-3225] Optimize TermsEnum.seek when caller doesn't need next term

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 4.0-ALPHA
• Lucene Fields: New
• Assignee: Michael McCandless
• Reporter: Michael McCandless
• Created: 21/Jun/11 22:12
• Updated: 28/Aug/22 12:50
• Resolved: 26/Jun/11 13:34

Description

Some codecs are able to save CPU if the caller is only interested in
exact matches. EG, Memory codec and SimpleText can do more efficient
FSTEnum lookup if they know the caller doesn't need to know the term
following the seek term.

We have cases like this in Lucene, eg when IW deletes documents by
Term, if the term is not found in a given segment then it doesn't need
to know the ceiling term. Likewise when TermQuery looks up the term
in each segment.

I had done this change as part of LUCENE-3030, which is a new terms
index that's able to save seeking for exact-only lookups, but now that
we have Memory codec that can also save CPU I think we should commit
this today.

The change adds a "boolean onlyExact" param to seek(BytesRef).