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