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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-448) optional norms
Date Wed, 26 Oct 2005 21:46:55 GMT
    [ http://issues.apache.org/jira/browse/LUCENE-448?page=comments#action_12356017 ] 

Doug Cutting commented on LUCENE-448:
-------------------------------------

+1

This can greatly reduce the amount of memory used by indexes with lots of fields.

It might be nice to add something like a Field.Index.NO_NORMS, that assumes un-tokenized...

> optional norms
> --------------
>
>          Key: LUCENE-448
>          URL: http://issues.apache.org/jira/browse/LUCENE-448
>      Project: Lucene - Java
>         Type: New Feature
>   Components: Index
>     Versions: CVS Nightly - Specify date in submission
>     Reporter: Yonik Seeley
>  Attachments: omitNorms.txt
>
> For applications with many indexed fields, the norms cause memory problems both during
indexing and querying.
> This patch makes norms optional on a per-field basis, in the same way that term vectors
are optional per-field.
> Overview of changes:
>  - Field.omitNorms that defaults to false
>  - backward compatible lucene file format change: FieldInfos.FieldBits has a bit for
omitNorms
>  - IndexReader.hasNorms() method
>  - During merging, if any segment includes norms, then norms are included.
>  - methods to get norms return the equivalent 1.0f array for backward compatibility
> The patch was designed for backward compatibility:
>  - all current unit tests pass w/o any modifications required
>  - compatible with old indexes since the default is omitNorms=false
>  - compatible with older/custom subclasses of IndexReader since a default hasNorms()
is provided
>  - compatible with older/custom users of IndexReader such as Weight/Scorer/explain since
a norm array is produced on demand, even if norms were not stored
> If this patch is accepted (or if the direction is acceptable), performance for scoring
 could be improved by assuming 1.0f when hasNorms(field)==false.

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