[jira] [Resolved] (LUCENE-3957) Document precision requirements of setBoost calls

["Adrien Grand (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/LUCENE-3957?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Adrien Grand resolved LUCENE-3957.
----------------------------------
    Resolution: Invalid

We don't support index-time boosts anymore.

> Document precision requirements of setBoost calls
> -------------------------------------------------
>
>                 Key: LUCENE-3957
>                 URL: https://issues.apache.org/jira/browse/LUCENE-3957
>             Project: Lucene - Core
>          Issue Type: Improvement
>          Components: general/javadocs
>    Affects Versions: 3.5
>            Reporter: Jordi Salvat i Alabart
>            Priority: Major
>
> The behaviour of index-time boosts seems pretty erratic (e.g. a boost of 8.0 produces the exact same score as a boost of 9.0) until you become aware that these factors end up encoded in a single byte, with a three-bit mantissa. This consumed a whole day of research for us, and I still believe we were lucky to spot it, given how deeply dug into the code & documentation this information is.
> I suggest adding a small note to the JavaDoc of setBoost methods in Document, Fieldable, FieldInvertState, and possibly AbstractField, Field, and NumericField.
> Suggested text:
> "Note that all index-time boost values end up encoded using Similarity.encodeNormValue, with a 3-bit mantissa -- so differences in the boost value of less than 25% may easily be rounded away."



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