amogh-jahagirdar commented on code in PR #4578:
URL: https://github.com/apache/iceberg/pull/4578#discussion_r873090308
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core/src/main/java/org/apache/iceberg/RemoveSnapshots.java:
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@@ -155,27 +168,93 @@ public List<Snapshot> apply() {
TableMetadata updated = internalApply();
List<Snapshot> removed = Lists.newArrayList(base.snapshots());
removed.removeAll(updated.snapshots());
-
return removed;
}
private TableMetadata internalApply() {
this.base = ops.refresh();
+ if (base.refs().isEmpty()) {
+ return base;
+ }
Set<Long> idsToRetain = Sets.newHashSet();
- List<Long> ancestorIds = SnapshotUtil.ancestorIds(base.currentSnapshot(),
base::snapshot);
- if (minNumSnapshots >= ancestorIds.size()) {
- idsToRetain.addAll(ancestorIds);
- } else {
- idsToRetain.addAll(ancestorIds.subList(0, minNumSnapshots));
+ // Identify refs that should be removed
+ Map<String, SnapshotRef> retainedRefs = computeRetainedRefs(base.refs());
+ Set<Long> retainedRefIds = retainedRefs.entrySet().stream()
+ .map(refEntry -> refEntry.getValue().snapshotId())
+ .collect(Collectors.toSet());
+
+ for (long idToRemove : idsToRemove) {
+ Preconditions.checkArgument(!retainedRefIds.contains(idToRemove),
+ "Cannot expire %s. There is a reference to it", idToRemove);
Review Comment:
There can be multiple references to the given idToRemove; so to get this
information the grouping from retained snapshot id to the list of refs has to
be computed. I do think the extra computation is worth it, it is odd to to
throw an exception "There is a reference to it" without mentioning what the
references are.
Will update to include the refs in the message. I think the message can
contain list of refs for the given id directly, I think in practice there would
not be so many refs for a given snapshot id that it would pollute the logs to
log it.
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