ChrisHegarty commented on code in PR #13570:
URL: https://github.com/apache/lucene/pull/13570#discussion_r1691039509
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lucene/core/src/java/org/apache/lucene/store/MMapDirectory.java:
##########
@@ -83,6 +94,41 @@ public class MMapDirectory extends FSDirectory {
*/
public static final BiPredicate<String, IOContext> NO_FILES = (filename,
context) -> false;
+ /**
+ * This sysprop allows to control the total maximum number of mmapped files
that can be associated
+ * with a single shared {@link java.lang.foreign.Arena foreign Arena}. For
example, to set the max
+ * number of permits to 256, pass the following on the command line pass
{@code
+ * -Dorg.apache.lucene.store.MMapDirectory.sharedArenaMaxPermits=256}.
Setting a value of 1
+ * associates one file to one shared arena.
+ *
+ * @lucene.internal
+ */
+ public static final String SHARED_ARENA_MAX_PERMITS_SYSPROP =
+ "org.apache.lucene.store.MMapDirectory.sharedArenaMaxPermits";
+
+ /** Argument for {@link #setGroupingFunction(Function)} that configures no
grouping. */
+ public static final Function<String, Optional<String>> NO_GROUPING =
filename -> Optional.empty();
+
+ /** Argument for {@link #setGroupingFunction(Function)} that configures
grouping by segment. */
+ public static final Function<String, Optional<String>> GROUP_BY_SEGMENT =
+ filename -> {
+ if (!CODEC_FILE_PATTERN.matcher(filename).matches()) {
+ return Optional.empty();
+ }
+ String groupKey =
IndexFileNames.parseSegmentName(filename).substring(1);
+ try {
+ // keep the original generation (=0) in base group, later
generations in extra group
+ if (IndexFileNames.parseGeneration(filename) > 0) {
+ groupKey += "-g";
+ }
+ } catch (
+ @SuppressWarnings("unused")
+ NumberFormatException unused) {
+ // does not confirm to the generation syntax, or trash
Review Comment:
Right. After we noticed this, we added a unit test to cover the back compat
scenario too. 👍
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