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Date: Wed, 17 Feb 2010 10:55:27 +0000 (UTC)
From: "Michael McCandless (JIRA)" <jira@apache.org>
To: java-dev@lucene.apache.org
Subject: [jira] Commented: (LUCENE-1761) low level Field metadata is never
 removed from index
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    [ 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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