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

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

amogh-jahagirdar commented on code in PR #6090:
URL: https://github.com/apache/iceberg/pull/6090#discussion_r1012465971


##########
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());
+      }
+    }
+    return expiredStatisticsFilesLocations;
+  }

Review Comment:
   Curious, is it guaranteed that StatisticsFIles cannot be reused across multiple snapshots? 
   The comment on StatisticsFile#snapshotId says 
   
   `  /** ID of the Iceberg table's snapshot the statistics were computed from. */
     long snapshotId();
   `
   Is it possible that a StatisticsFile "file1" is computed at snapshot 1, but then still considered a valid reachable statistics file at Snapshot 2? and then we wouldn't want to do a removal of that file.
   
   If it is possible it seems that we need to capture the reachability set rather than just removing all the statistics file before expiration. let me know if i misunderstood ! 



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