RussellSpitzer commented on a change in pull request #3039:
URL: https://github.com/apache/iceberg/pull/3039#discussion_r765243781
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File path: core/src/main/java/org/apache/iceberg/util/SnapshotUtil.java
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@@ -101,6 +101,53 @@ public static Snapshot oldestAncestor(Table table) {
return ancestorsOf(start, lookup);
}
+ /**
+ * Traverses the history of the table's current snapshot
+ * and finds the oldest ancestor snapshot after or equal to the timestamp in
milliseconds.
+ *
+ * @param table a table
+ * @param timestampMillis a timestamp in milliseconds
+ * @return the first snapshot from the given timestamp, or null if the
current snapshot is older than the timestamp
+ * @throws IllegalStateException if the first snapshot from the given time
can't be determined
+ */
+ public static Snapshot oldestAncestorFrom(Table table, Long timestampMillis)
{
+ Snapshot currentSnapshot = table.currentSnapshot();
+ long timestamp = timestampMillis == null ? -1L : timestampMillis;
+ // If no snapshot exists or timestamp is higher than the current snapshot
+ if (currentSnapshot == null || currentSnapshot.timestampMillis() <
timestamp) {
+ return null;
+ }
+
+ // Traverse to the oldest snapshot after or equal to the timestamp
Review comment:
So If I have this right the method is basically (assuming ordered by
timestamp)
StreamSupport.stream(currentAncestors(table).spliterator(), false)
.filter(snapshot -> snapshot.timestampMillis() >= targetTimestamp)
// For elements that are as new as or newer than the target
.reduce((first, second) -> second) // Return the last element we see
(although a boolean could be put in here to select the oldest of first and
second if ordering of currentAncestors is not guaranteed ... I think it is
though)
.orElse(null);
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