jpountz commented on code in PR #13998:
URL: https://github.com/apache/lucene/pull/13998#discussion_r1850224848
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lucene/core/src/java21/org/apache/lucene/store/MemorySegmentIndexInput.java:
##########
@@ -406,6 +406,15 @@ void advise(long offset, long length,
IOConsumer<MemorySegment> advice) throws I
}
}
+ public Optional<Boolean> isLoaded() {
Review Comment:
Is it missing the `@Override` annotation?
##########
lucene/core/src/java/org/apache/lucene/store/IndexInput.java:
##########
@@ -226,4 +227,17 @@ public String toString() {
* @param length the number of bytes to prefetch
*/
public void prefetch(long offset, long length) throws IOException {}
+
+ /**
+ * Returns a hint whether all the contents of this input are resident in
physical memory. It's a
+ * hint because the operating system may have paged out some of the data by
the time this method
+ * returns. If the optional is true, then it's likely that the contents of
this input are resident
+ * in physical memory. A value of false does not imply that the contents are
not resident in
+ * physical memory. An empty optional is returned if it is not possible to
determine.
Review Comment:
It looks like an empty optional and `false` mostly mean the same thing,
which makes me wonder if this should return a `boolean` directly?
It may also be worth pointing out that this method runs in linear time with
the amount of data that this `IndexInput` exposes (as opposed to
constant-time). So it makes little sense to use it to do something like "if
(isLoaded() == false) { prefetch(); }"
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