abhishekagarwal87 commented on a change in pull request #11398:
URL: https://github.com/apache/druid/pull/11398#discussion_r668635537
##########
File path:
server/src/main/java/org/apache/druid/segment/loading/SegmentLoader.java
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@@ -29,10 +30,45 @@
* Loading segments from deep storage to local storage.
* Implementations must be thread-safe.
*/
+@UnstableApi
public interface SegmentLoader
{
boolean isSegmentLoaded(DataSegment segment);
- Segment getSegment(DataSegment segment, boolean lazy,
SegmentLazyLoadFailCallback loadFailed) throws SegmentLoadingException;
+
+ /**
+ * Returns a {@link ReferenceCountingSegment} that will be added by the
{@link org.apache.druid.server.SegmentManager}
+ * to the {@link org.apache.druid.timeline.VersionedIntervalTimeline}. This
method can be called multiple times
+ * by the {@link org.apache.druid.server.SegmentManager}
+ *
+ * Returning a {@code ReferenceCountingSegment} will let custom
implementations keep track of reference count for
+ * segments that the custom implementations are creating. That way, custom
implementations can know when the segment
+ * is in use or not.
+ * @param segment - {@link DataSegment} segment to download
+ * @param lazy - whether the loading is lazy
+ * @param loadFailed - Callback to invoke if the loading fails
+ * @return Segment object wrapped inside {@link ReferenceCountingSegment}.
+ * @throws SegmentLoadingException
+ */
+ ReferenceCountingSegment getSegment(DataSegment segment, boolean lazy,
SegmentLazyLoadFailCallback loadFailed) throws SegmentLoadingException;
Review comment:
It can do either and the caller is not supposed to depend on that
behavior. From the caller's perspective, it is going to get a segment object
wrapped inside `ReferenceCountingSegment`. Implementations can have
optimizations to save on repeated expensive work.
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