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From "Michael McCandless (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-1761) low level Field metadata is never removed from index
Date Wed, 17 Feb 2010 10:55:27 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-1761?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12834730#action_12834730
] 

Michael McCandless commented on LUCENE-1761:
--------------------------------------------

I don't think there will be much perf loss.  Each dead field will cause a FieldInfo instance
to be created (which is very small).

Norms won't be loaded unless something explicitly asks for them.  EG if you do a search against
the dead field, that will create the 1 byte per doc array.  If you do a sort against the dead
field, FieldCache will be populated (which is silly since the values will all be null/0).
 But if no searching is done against the fields I believe there's very little cost.

But we really should fix merging to purge fields that don't occur anymore...

> low level Field metadata is never removed from index
> ----------------------------------------------------
>
>                 Key: LUCENE-1761
>                 URL: https://issues.apache.org/jira/browse/LUCENE-1761
>             Project: Lucene - Java
>          Issue Type: Bug
>          Components: Index
>    Affects Versions: 2.2, 2.3, 2.3.1, 2.3.2, 2.4, 2.4.1
>            Reporter: Hoss Man
>            Priority: Minor
>         Attachments: LUCENE-1761.patch
>
>
> with heterogeneous docs, or an index whose fields evolve over time, field names that
are no longer used (ie: all docs that ever referenced them have been deleted) still show up
when you use IndexReader.getFieldNames.
> It seems logical that segment merging should only preserve metadata about fields that
actually existing the new segment, but even after deleting all documents from an index and
optimizing the old field names are still present.

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