pvary commented on code in PR #12629:
URL: https://github.com/apache/iceberg/pull/12629#discussion_r2016500323


##########
core/src/main/java/org/apache/iceberg/PartitionStatsUtil.java:
##########
@@ -45,22 +49,53 @@ private PartitionStatsUtil() {}
    * @param table the table for which partition stats to be computed.
    * @param snapshot the snapshot for which partition stats is computed.
    * @return the collection of {@link PartitionStats}
+   * @deprecated since 1.9.0, will be removed in 1.10.0; use {@link 
#computeStats(Table, Snapshot,
+   *     Snapshot)} instead.
    */
+  @Deprecated
   public static Collection<PartitionStats> computeStats(Table table, Snapshot 
snapshot) {
-    Preconditions.checkArgument(table != null, "table cannot be null");
-    Preconditions.checkArgument(Partitioning.isPartitioned(table), "table must 
be partitioned");
-    Preconditions.checkArgument(snapshot != null, "snapshot cannot be null");
+    return computeStats(table, null, snapshot).values();
+  }
 
-    StructType partitionType = Partitioning.partitionType(table);
-    List<ManifestFile> manifests = snapshot.allManifests(table.io());
-    Queue<PartitionMap<PartitionStats>> statsByManifest = 
Queues.newConcurrentLinkedQueue();
-    Tasks.foreach(manifests)
-        .stopOnFailure()
-        .throwFailureWhenFinished()
-        .executeWith(ThreadPools.getWorkerPool())
-        .run(manifest -> statsByManifest.add(collectStats(table, manifest, 
partitionType)));
+  /**
+   * Computes the partition stats incrementally after the given snapshot to 
current snapshot. If the
+   * given snapshot is null, computes the stats completely instead of 
incrementally.
+   *
+   * @param table the table for which partition stats to be computed.
+   * @param fromSnapshot the snapshot after which partition stats is computed 
(exclusive).
+   * @param currentSnapshot the snapshot till which partition stats is 
computed (inclusive).
+   * @return the {@link PartitionMap} of {@link PartitionStats}
+   */
+  public static PartitionMap<PartitionStats> computeStats(
+      Table table, Snapshot fromSnapshot, Snapshot currentSnapshot) {
+    Preconditions.checkArgument(table != null, "Table cannot be null");
+    Preconditions.checkArgument(Partitioning.isPartitioned(table), "Table must 
be partitioned");
+    Preconditions.checkArgument(currentSnapshot != null, "Current snapshot 
cannot be null");
 
-    return mergeStats(statsByManifest, table.specs());
+    Predicate<ManifestFile> manifestFilePredicate = file -> true;
+    if (fromSnapshot != null) {
+      Preconditions.checkArgument(currentSnapshot != fromSnapshot, "Both the 
snapshots are same");
+      Preconditions.checkArgument(
+          SnapshotUtil.isAncestorOf(table, currentSnapshot.snapshotId(), 
fromSnapshot.snapshotId()),
+          "Starting snapshot %s is not an ancestor of current snapshot %s",
+          fromSnapshot.snapshotId(),
+          currentSnapshot.snapshotId());
+      Set<Long> snapshotIdsRange =
+          Sets.newHashSet(
+              SnapshotUtil.ancestorIdsBetween(
+                  currentSnapshot.snapshotId(), fromSnapshot.snapshotId(), 
table::snapshot));
+      manifestFilePredicate =
+          manifestFile ->
+              snapshotIdsRange.contains(manifestFile.snapshotId())
+                  && !manifestFile.hasExistingFiles();

Review Comment:
   What do we do with the stats of the removed files?
   
   Lets say:
   - S1 adds data
   - Execute the stats collection
   - S2 adds more data
   - S3 compacts data from S1, and S2 - This removes files created by S1, and 
S2 and creates new files
   - Execute incremental/normal stats collection
   
   What happens with the stats in this case?



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