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

[Sanne Grinovero (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HSEARCH-135?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_29575 ] 

Sanne Grinovero commented on HSEARCH-135:
-----------------------------------------

Did you try to compare RAMDirectory performance to FSDirectory performance?
The filesystem is just slower the first time you have to read a segment/sector, after that the operating system knows some very good tricks about I/O optimization given enough free ram and you don't have to care (much) about memory requirements or have more work for your garbage collector.
Also the OS is quite good at giving you transparently the correct version, so avoiding all the mess with flushing and reloading.
My tests run on linux, but I think other oses should behave similarly.

You can still get "the best of both worlds" with indexreader "warmup", having some query hit most segments in background before returning it to real searchers. Of course, this is only possible if you can somehow prepare the indexreaders beforehand.

> 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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