[GitHub] [iceberg] zhengzengprc commented on a change in pull request #3039: Introduce spark3 option to read stream from a timestamp

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zhengzengprc commented on a change in pull request #3039:
URL: https://github.com/apache/iceberg/pull/3039#discussion_r749815932



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File path: core/src/main/java/org/apache/iceberg/util/SnapshotUtil.java
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@@ -65,12 +65,18 @@ public static boolean ancestorOf(Table table, long snapshotId, long ancestorSnap
   }
 
   /**
-   * Traverses the history of the table's current snapshot and finds the oldest Snapshot.
-   * @return null if there is no current snapshot in the table, else the oldest Snapshot.
+   * Traverses the history of the table's current snapshot
+   * and finds the oldest Snapshot after or equal to the timestamp in milliseconds.
+   * @return null if there is no current snapshot in the table,
+   * else the oldest Snapshot after or equal to the timestamp in milliseconds.
    */
-  public static Snapshot oldestSnapshot(Table table) {
+  public static Snapshot oldestSnapshot(Table table, long timestampMillis) {

Review comment:
       Thanks @rdblue, it is a very interesting problem to handle the expired snapshot. I can reproduce the problem in unit test. I am thinking about it is better way to loop the snapshots without the parentId
   `  public static Snapshot snapshotAfter(Table table, long snapshotId) {
       Preconditions.checkArgument(table.snapshot(snapshotId) != null, "Cannot find parent snapshot: %s", snapshotId);
   
       Snapshot current = table.currentSnapshot();
       while (current != null) {
         if (current.parentId() == snapshotId) {
           return current;
         }
   
         current = table.snapshot(current.parentId());
       }
   
       throw new IllegalStateException(
           String.format("Cannot find snapshot after %s: not an ancestor of table's current snapshot", snapshotId));
     }`
   It seems like we have similar issue with the above code block when some of the previous snapshot expired




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