[LUCENE-1612] expose lastDocId in the posting from the TermEnum API

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Invalid
• Affects Version/s: 2.4
• Component/s: core/index
• Lucene Fields: New, Patch Available
• Assignee: Unassigned
• Reporter: John Wang
• Created: 25/Apr/09 03:01
• Updated: 28/Aug/22 12:00
• Resolved: 22/Feb/13 05:49

Description

We currently have on the TermEnum api: docFreq() which gives the number docs in the posting.
It would be good to also have the max docid in the posting. That information is useful when construction a custom DocIdSet, .e.g determine sparseness of the doc list to decide whether or not to use a BitSet.

I have written a patch to do this, the problem with it is the TermInfosWriter encodes values in VInt/VLong, there is very little flexibility to add in lastDocId while making the index backward compatible. (If simple int is used for say, docFreq, a bit can be used to flag reading of a new piece of information)

output.writeVInt(ti.docFreq); // write doc freq
output.writeVLong(ti.freqPointer - lastTi.freqPointer); // write pointers
output.writeVLong(ti.proxPointer - lastTi.proxPointer);

Anyway, patch is attached with:TestSegmentTermEnum modified to test this. TestBackwardsCompatibility fails due to reasons described above.