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From "Stephen Bochinski (JIRA)" <>
Subject [jira] Commented: (SOLR-1961) Use Lucene's Field Cache To Retrieve Stored Fields From Memory
Date Mon, 28 Jun 2010 20:52:51 GMT


Stephen Bochinski commented on SOLR-1961:

Forgot to remove those TODO's. I'll remove them when I update the patch as well as adding
the ASL stuff. 

I don't have any unit tests written so far. I will write some and include them in the updated

> Use Lucene's Field Cache To Retrieve Stored Fields From Memory
> --------------------------------------------------------------
>                 Key: SOLR-1961
>                 URL:
>             Project: Solr
>          Issue Type: New Feature
>          Components: search
>    Affects Versions: 1.4
>            Reporter: Stephen Bochinski
>         Attachments: patch.txt
>   Original Estimate: 101.5h
>  Remaining Estimate: 101.5h
> This allows the user to configure which fields should be field cached in the schema.xml
file by adding the following attribute:
> fieldCached="true"
> Enabling this on a field greatly decreases the time needed to retrieve stored fields.
This works on fields containing Bytes, Strings, Integers, Longs, and Floats. Enabling field
cache is applicable in many scenarios. For instance, if you have a bunch of text that is indexed
and not stored and you only need to retrieve a string or number associated with a document.
Its applicable in any case where there are many indexed fields and not too many stored fields
being retrieved. The memory consumption is not very high compared to the performance gains
field cache brings.
> Memory consumption is governed by: Number of fields cached * Number of documents *  8
bytes per reference +
> 	SUM(Number of unique values of the field  * average length of term)  * 2 (chars use
2 bytes) * String overhead (40 bytes)

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