RussellSpitzer commented on a change in pull request #3775:
URL: https://github.com/apache/iceberg/pull/3775#discussion_r772032673
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File path: core/src/main/java/org/apache/iceberg/util/SnapshotUtil.java
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@@ -102,43 +102,35 @@ public static Snapshot oldestAncestor(Table table) {
}
/**
- * Traverses the history of the table's current snapshot and:
- * 1. returns null, if no snapshot exists or target timestamp is more recent
than the current snapshot.
- * 2. else return the first snapshot which satisfies {@literal >=}
targetTimestamp.
- * <p>
- * Given the snapshots (with timestamp): [S1 (10), S2 (11), S3 (12), S4 (14)]
- * <p>
- * firstSnapshotAfterTimestamp(table, x {@literal <=} 10) = S1
- * firstSnapshotAfterTimestamp(table, 11) = S2
- * firstSnapshotAfterTimestamp(table, 13) = S4
- * firstSnapshotAfterTimestamp(table, 14) = S4
- * firstSnapshotAfterTimestamp(table, x {@literal >} 14) = null
- * <p>
- * where x is the target timestamp in milliseconds and Si is the snapshot
+ * Traverses the history of the table's current snapshot and finds the first
snapshot after the given timestamp.
*
* @param table a table
- * @param targetTimestampMillis a timestamp in milliseconds
- * @return the first snapshot which satisfies {@literal >=} targetTimestamp,
or null if the current snapshot is
- * more recent than the target timestamp
+ * @param timestampMillis a timestamp in milliseconds
+ * @return the first snapshot after the given timestamp, or null if the
current snapshot is older than the timestamp
+ * @throws IllegalStateException if the first ancestor after the given time
can't be determined
*/
- public static Snapshot firstSnapshotAfterTimestamp(Table table, Long
targetTimestampMillis) {
- Snapshot currentSnapshot = table.currentSnapshot();
- // Return null if no snapshot exists or target timestamp is more recent
than the current snapshot
- if (currentSnapshot == null || currentSnapshot.timestampMillis() <
targetTimestampMillis) {
+ public static Snapshot oldestAncestorAfter(Table table, long
timestampMillis) {
+ if (table.currentSnapshot() == null) {
+ // there are no snapshots or ancestors
return null;
}
- // Return the oldest snapshot which satisfies >= targetTimestamp
Snapshot lastSnapshot = null;
for (Snapshot snapshot : currentAncestors(table)) {
- if (snapshot.timestampMillis() < targetTimestampMillis) {
+ if (snapshot.timestampMillis() <= timestampMillis) {
return lastSnapshot;
}
+
lastSnapshot = snapshot;
}
- // Return the oldest snapshot if the target timestamp is less than the
oldest snapshot of the table
- return lastSnapshot;
+ if (lastSnapshot != null && lastSnapshot.parentId() == null) {
+ // this is the first snapshot in the table, return it
Review comment:
I am a little worried about having a function which works for a given
input but only until the starting snapshot is expired. For example
```
oldestAncestorAfter(table, Long.MinValue) // Returns first snapshot
expireSnapshots() // Expire first snapshot
oldestAncestorAfter(table, Long.MinValue) // Throws exception
```
I think if we want to standardize this should probably also throw an
exception
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