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https://issues.apache.org/jira/browse/LUCENE-1612?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12702829#action_12702829
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Michael McCandless commented on LUCENE-1612:
--------------------------------------------

Actually I think the codec will handle merging (this was recently proposed for 
payloads), so it should be able to do that optimization within itself.

> 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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