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https://issues.apache.org/jira/browse/LUCENE-8635?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16756098#comment-16756098
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Mike Sokolov edited comment on LUCENE-8635 at 1/30/19 1:24 PM:
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I agree that would be a good start. Perhaps as a separate issue we can add
finer per-field control of when to use on vs off-heap (per field, eg).
Just to look a little way down that path: It seems that the nearest thing to do
this today is {{get/setPreload()}} and {{get/setUseUnmap}} in
{{MMapDirectory}}, but here one really wants a mapping by field name, and a
Directory should not really bne concerned with field names. Better would be an
attribute of {{FieldInfo}}, where we have {{put/getAttribute}}. Then
{{FieldReader}} can inspect the {{FieldInfo}} and pass the appropriate
{{On/OffHeapStore}} when creating its {{FST}}. What do you think?
was (Author: sokolov):
I agree that would be a good start. Perhaps as a separate issue we can add
finer per-field control of when to use on vs off-heap (per field, eg).
Just to look a little way down that path: It seems that the nearest thing to do
this today is {{get/setPreload()}} and {{get/setUseUnmap}} in
{{MMapDirectory}}, but here one really wants a mapping by field name, and a
Directory should not really bne concerned with field names. Better would be an
attribute of {{FieldInfo}}, where we have {{put/getAttribute}}. Then
{{FieldReader}} can inspect the {{FieldInfo}} and pass the appropriate
{{On/OffHeapStore}} when creating its {{FST}}.
> 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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