[hibernate-issues] [Hibernate-JIRA] Commented: (HSEARCH-135) Create a RAMDirectoryProvider from an existing Lucene FSDirectory

[Hardy Ferentschik (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HSEARCH-135?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_28982 ] 

Hardy Ferentschik commented on HSEARCH-135:
-------------------------------------------

I posted a question onto the Lucene forum. Here is the answer (http://www.gossamer-threads.com/lists/lucene/java-user/55100):

> one can improve search performance by using a RAMDirectory created
from an underlying FSDirectory using one of the parameterised
constructors. Is this correct?
Absolutly
 
> Will a FSDirectory not automatically load the index into memory
provided enough RAM is available?  
Not all index files are loaded in the RAM if you are using the
FSDirectory. Though at the same time, queries are cached.
 
> Do I have to explicitly use a RAMDirectory?
If you want to load the comeplte index in the memory, yes. This increase
the performance a lot as it drastically reduces the number of disk IO.
Obviously at the cost of the RAM. If you have enough RAM available to
accommodate the complete index, you can go ahead with this

> Create a RAMDirectoryProvider from an existing Lucene FSDirectory
> -----------------------------------------------------------------
>
>                 Key: HSEARCH-135
>                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HSEARCH-135
>             Project: Hibernate Search
>          Issue Type: New Feature
>          Components: directory provider
>            Reporter: Hardy Ferentschik
>
> It would be nice to have the ability to use a Lucene RAM index which gets constucted from an existing Lucene file based indexed. For example in an JMS setup the master could create a file based Lucene index, share it out to the slaves which in turn use this file based index to populate a RAM index. This would give you the best of two worlds. 
> Not sure how hard it would be to implement this in an unclustered environment.

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