uschindler commented on code in PR #13570:
URL: https://github.com/apache/lucene/pull/13570#discussion_r1679741852
##########
lucene/core/src/java21/org/apache/lucene/store/MemorySegmentIndexInputProvider.java:
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@@ -125,4 +134,31 @@ private final MemorySegment[] map(
}
return segments;
}
+
+ public ConcurrentHashMap<String, RefCountedSharedArena> attachment() {
+ return new ConcurrentHashMap<>();
+ }
+
+ /**
+ * Gets an arena for the give path, potentially aggregating files from the
same segment into a
+ * single ref counted shared arena. A ref counted shared arena, if created
will be added to the
+ * given arenas map.
+ */
+ static Arena getSharedArena(Path p, ConcurrentHashMap<String,
RefCountedSharedArena> arenas) {
+ String filename = p.getFileName().toString();
+ String segmentName = IndexFileNames.parseSegmentName(filename);
+ if (filename.length() == segmentName.length()) {
+ // no segment found; just use a shared segment
+ return Arena.ofShared();
Review Comment:
The case you are looking here at is when there is no relationship to a
specific segment of an index. If it is a file which does not belong to a
segment it returns a new shared arena (fallback to default). For this case it
MUST return a new shared segment as the file belongs to nothing else and the
mmapped memory must be freed on close.
If the file belongs to an index segment it also creates a shared arena for
the first file, but other files belonging to same segment will increase
refcount. For that it has its own implementation of Arena which includes
refcounting.
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