[ http://issues.apache.org/jira/browse/LUCENE-448?page=all ]
Yonik Seeley updated LUCENE-448:
--------------------------------
Attachment: omitNorms.txt
> 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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