[GitHub] [iceberg] ajantha-bhat commented on a diff in pull request #3457: Spark: Improve performance of expire snapshot by not double-scanning retained Snapshots

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

ajantha-bhat commented on code in PR #3457:
URL: https://github.com/apache/iceberg/pull/3457#discussion_r933720884


##########
spark/v3.2/spark/src/main/java/org/apache/iceberg/spark/actions/ExpireSnapshotsSparkAction.java:
##########
@@ -222,13 +228,34 @@ private ExpireSnapshots.Result doExecute() {
     }
   }
 
+  /**
+   * Builds a dataset of reachable files from given table metadata
+   *
+   * @param metadata table metadata
+   * @return a dataset of files: schema(file_path, file_type)
+   */
   private Dataset<Row> buildValidFileDF(TableMetadata metadata) {
     Table staticTable = newStaticTable(metadata, table.io());
     return buildValidContentFileWithTypeDF(staticTable)
         .union(withFileType(buildManifestFileDF(staticTable), MANIFEST))
         .union(withFileType(buildManifestListDF(staticTable), MANIFEST_LIST));
   }
 
+  /**
+   * Builds a dataset of reachable files from given table metadata, with a snapshot filter
+   *
+   * @param metadata table metadata
+   * @param snapshotsToExclude files reachable by this snapshot will be filtered out
+   * @return a dataset of files: schema(file_path, file_type)
+   */
+  private Dataset<Row> buildFilteredValidDataDF(
+      TableMetadata metadata, Set<Long> snapshotsToExclude) {
+    Table staticTable = newStaticTable(metadata, table.io());
+    return buildValidContentFileWithTypeDF(staticTable, snapshotsToExclude)

Review Comment:
   > Yes, I think there was a proposal for that by @ajantha-bhat https://github.com/apache/iceberg/pull/4674, we werent sure that caching is worth the cost (it may involves an extra read-write)
   
   I didn't find so much performance difference when tested locally. Hence, I didn't proceed further on #4674. May be I need to Test in S3 to really see the benefit. 



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