[GitHub] [iceberg] findepi commented on a diff in pull request #6090: Core: Handle statistics file clean up from expireSnapshots

[GitBox <gi...@apache.org>]

findepi commented on code in PR #6090:
URL: https://github.com/apache/iceberg/pull/6090#discussion_r1013923155


##########
core/src/main/java/org/apache/iceberg/FileCleanupStrategy.java:
##########
@@ -79,4 +80,15 @@ protected void deleteFiles(Set<String> pathsToDelete, String fileType) {
             (file, thrown) -> LOG.warn("Delete failed for {} file: {}", fileType, file, thrown))
         .run(deleteFunc::accept);
   }
+
+  protected Set<String> expiredStatisticsFilesLocations(
+      TableMetadata beforeExpiration, Set<Long> expiredIds) {
+    Set<String> expiredStatisticsFilesLocations = Sets.newHashSet();
+    for (StatisticsFile statisticsFile : beforeExpiration.statisticsFiles()) {
+      if (expiredIds.contains(statisticsFile.snapshotId())) {
+        expiredStatisticsFilesLocations.add(statisticsFile.path());

Review Comment:
   - `statisticsFile.snapshotId()` is "ID of the Iceberg table's snapshot the statistics were computed from",  it's not "ID of the snapshot the file is attached to"
   - The spec allows one Puffin file to be attached to multiple snapshots. For example, rewrite_files / optimize will produce a new snapshot, but could carry forward some/all table-level stats.
     - So, the fact that the snapshot is being forgotten doesn't imply the stats file can be safely deleted.



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