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Posted to dev@lucene.apache.org by "Michael McCandless (JIRA)" <ji...@apache.org> on 2009/04/25 11:33:30 UTC
[jira] Commented: (LUCENE-1612) expose lastDocId in the posting
from the TermEnum API
[ https://issues.apache.org/jira/browse/LUCENE-1612?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12702669#action_12702669 ]
Michael McCandless commented on LUCENE-1612:
--------------------------------------------
This would be a good test (custom codec) for flexible indexing (LUCENE-1458), ie, allowing you to write whatever you want per-term.
Also, if lastDocID is always available, this could make merging of postings much faster than it is today, because you could bulk-copy the doc/freq posting bytes while just "fixing up" the boundary between them, because docIDs are delta coded.
> expose lastDocId in the posting from the TermEnum API
> -----------------------------------------------------
>
> Key: LUCENE-1612
> URL: https://issues.apache.org/jira/browse/LUCENE-1612
> Project: Lucene - Java
> Issue Type: Improvement
> Components: Index
> Affects Versions: 2.4
> Reporter: John Wang
> Attachments: lucene-1612-patch.txt
>
>
> 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.
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