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From "Stephen Bochinski (JIRA)" <j...@apache.org>
Subject [jira] Created: (SOLR-1961) Use Lucene's Field Cache To Retrieve Stored Fields From Memory
Date Thu, 17 Jun 2010 23:31:23 GMT
Use Lucene's Field Cache To Retrieve Stored Fields From Memory
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                 Key: SOLR-1961
                 URL: https://issues.apache.org/jira/browse/SOLR-1961
             Project: Solr
          Issue Type: New Feature
          Components: search
    Affects Versions: 1.4
            Reporter: Stephen Bochinski


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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