hemantk-12 commented on code in PR #6542:
URL: https://github.com/apache/ozone/pull/6542#discussion_r1568200387
##########
hadoop-ozone/ozone-manager/src/main/java/org/apache/hadoop/ozone/om/OmMetadataManagerImpl.java:
##########
@@ -1345,30 +1345,30 @@ public List<SnapshotInfo> listSnapshot(
} else {
// This allows us to seek directly to the first key with the right
prefix.
seek = getOzoneKey(volumeName, bucketName,
- StringUtil.isNotBlank(
- snapshotPrefix) ? snapshotPrefix : OM_KEY_PREFIX);
+ StringUtil.isNotBlank(snapshotPrefix) ? snapshotPrefix :
OM_KEY_PREFIX);
}
List<SnapshotInfo> snapshotInfos = Lists.newArrayList();
+ String lastSnapshot = null;
try (ListIterator.MinHeapIterator snapshotIterator =
- new ListIterator.MinHeapIterator(this, prefix, seek, volumeName,
- bucketName, snapshotInfoTable)) {
- try {
- while (snapshotIterator.hasNext() && maxListResult > 0) {
- SnapshotInfo snapshotInfo =
- (SnapshotInfo) snapshotIterator.next().getValue();
- if (!snapshotInfo.getName().equals(prevSnapshot)) {
- snapshotInfos.add(snapshotInfo);
- maxListResult--;
- }
+ new ListIterator.MinHeapIterator(this, prefix, seek, volumeName,
bucketName, snapshotInfoTable)) {
+ SnapshotInfo snapshotInfo = null;
+ while (snapshotIterator.hasNext() && maxListResult > 0) {
+ snapshotInfo = (SnapshotInfo) snapshotIterator.next().getValue();
+ if (!Objects.equals(snapshotInfo.getName(), prevSnapshot)) {
+ snapshotInfos.add(snapshotInfo);
+ maxListResult--;
}
- } catch (NoSuchElementException e) {
- throw new IOException(e);
- } catch (UncheckedIOException e) {
- throw e.getCause();
}
+ if (snapshotIterator.hasNext() && maxListResult == 0 && snapshotInfo !=
null) {
+ lastSnapshot = snapshotInfo.getName();
+ }
+ } catch (NoSuchElementException e) {
+ throw new IOException(e);
+ } catch (UncheckedIOException e) {
+ throw e.getCause();
}
- return snapshotInfos;
+ return new ListSnapshotResponse(snapshotInfos, lastSnapshot);
Review Comment:
You are right as of now.
One benefit, I see with passing `lastSnapshot` rather than boolean, is if we
change the key for the table (tho you can argue it is unlikely). Returning the
continuation token decouples the logic and can be changed at any time.
Returning the continuation is similar to standard pagination API e.g.
[DynamoDB](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Query.Pagination.html)
or
[api-pagination-best-practices-and-strategies](https://dev.to/pragativerma18/unlocking-the-power-of-api-pagination-best-practices-and-strategies-4b49)
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