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From "Michael McCandless (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-1604) Stop creating huge arrays to represent the absense of field norms
Date Mon, 27 Apr 2009 12:33:30 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-1604?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12703101#action_12703101
] 

Michael McCandless commented on LUCENE-1604:
--------------------------------------------


I tested this change on a Wikipedia index, with query "1", on a field
that has norms.

On Linux, JDK 1.6.0_13, I can see no performance difference (both get
7.2 qps, best of 10 runs).

On Mac OS X 10.5.6, I see some difference (13.0 vs 12.3, best of 10
runs), but given quirkiness I've seen on OS X's results not matching
other platforms, I think we can disgregard this.

Also, given the performance gain one sees when norms are disabled, I
think this is net/net a good change.

We'll leave the default as false (for back compat), but this setting
is deprecated with a comment that in 3.0 it hardwires to true.


> Stop creating huge arrays to represent the absense of field norms
> -----------------------------------------------------------------
>
>                 Key: LUCENE-1604
>                 URL: https://issues.apache.org/jira/browse/LUCENE-1604
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Index
>    Affects Versions: 2.9
>            Reporter: Shon Vella
>            Assignee: Michael McCandless
>            Priority: Minor
>             Fix For: 2.9
>
>         Attachments: LUCENE-1604.patch, LUCENE-1604.patch, LUCENE-1604.patch
>
>
> Creating and keeping around huge arrays that hold a constant value is very inefficient
both from a heap usage standpoint and from a localility of reference standpoint. It would
be much more efficient to use null to represent a missing norms table.

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