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https://issues.apache.org/jira/browse/LUCENE-8635?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16772167#comment-16772167
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ASF subversion and git services commented on LUCENE-8635:
---------------------------------------------------------

Commit 7b93dd5aa5016e4e4365b97439f406bc86cab451 in lucene-solr's branch 
refs/heads/branch_8_0 from Michael McCandless
[ https://gitbox.apache.org/repos/asf?p=lucene-solr.git;h=7b93dd5 ]

LUCENE-8635: add option to move FSTs off-heap, and do so for the FST terms 
index in the default codec for non-primary-key fields if MMapDirectory is being 
used


> Lazy loading Lucene FST offheap using mmap
> ------------------------------------------
>
>                 Key: LUCENE-8635
>                 URL: https://issues.apache.org/jira/browse/LUCENE-8635
>             Project: Lucene - Core
>          Issue Type: New Feature
>          Components: core/FSTs
>         Environment: I used below setup for es_rally tests:
> single node i3.xlarge running ES 6.5
> es_rally was running on another i3.xlarge instance
>            Reporter: Ankit Jain
>            Priority: Major
>         Attachments: fst-offheap-ra-rev.patch, fst-offheap-rev.patch, 
> offheap.patch, optional_offheap_ra.patch, ra.patch, rally_benchmark.xlsx
>
>
> Currently, FST loads all the terms into heap memory during index open. This 
> causes frequent JVM OOM issues if the term size gets big. A better way of 
> doing this will be to lazily load FST using mmap. That ensures only the 
> required terms get loaded into memory.
>  
> Lucene can expose API for providing list of fields to load terms offheap. I'm 
> planning to take following approach for this:
>  # Add a boolean property fstOffHeap in FieldInfo
>  # Pass list of offheap fields to lucene during index open (ALL can be 
> special keyword for loading ALL fields offheap)
>  # Initialize the fstOffHeap property during lucene index open
>  # FieldReader invokes default FST constructor or OffHeap constructor based 
> on fstOffHeap field
>  
> I created a patch (that loads all fields offheap), did some benchmarks using 
> es_rally and results look good.



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