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From "Michael McCandless (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-1476) BitVector implement DocIdSet
Date Fri, 16 Jan 2009 17:20:59 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-1476?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12664570#action_12664570
] 

Michael McCandless commented on LUCENE-1476:
--------------------------------------------

bq. Why? The returned iterator can traverse the multiple bitvectors.

Woops, sorry: I missed that it would return a DocIdSet (iterator only) vs underlying (current)
BitVector.  So then MultiReader could return a DocIdSet.

bq. If the segment is large, tombstones can solve this.

Right; I was saying, as things are today (single BitVector holds all deleted docs), one limitation
of the realtime approach we are moving towards is the copy-on-write cost of the first delete
on a freshly cloned reader for a large segment.

If we moved to using only iterator API for accessing deleted docs within Lucene then we could
explore fixes for the copy-on-write cost w/o changing on-disk representation of deletes. 
IE tombstones are perhaps overkill for Lucene, since we're not using the filesystem as the
intermediary for communicating deletes to a reopened reader.  We only need an in-RAM incremental
solution.

> BitVector implement DocIdSet
> ----------------------------
>
>                 Key: LUCENE-1476
>                 URL: https://issues.apache.org/jira/browse/LUCENE-1476
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Index
>    Affects Versions: 2.4
>            Reporter: Jason Rutherglen
>            Priority: Trivial
>         Attachments: LUCENE-1476.patch, quasi_iterator_deletions.diff
>
>   Original Estimate: 12h
>  Remaining Estimate: 12h
>
> BitVector can implement DocIdSet.  This is for making SegmentReader.deletedDocs pluggable.

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