[GitHub] [iceberg] rdblue commented on a change in pull request #2892: API: Add validation that delete file referenced files are not rewritten

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

rdblue commented on a change in pull request #2892:
URL: https://github.com/apache/iceberg/pull/2892#discussion_r680235789



##########
File path: core/src/test/java/org/apache/iceberg/TestRewriteFiles.java
##########
@@ -641,4 +641,115 @@ public void testNewDeleteFile() {
         .rewriteFiles(Sets.newSet(FILE_A), Sets.newSet(FILE_A2))
         .apply();
   }
+
+  @Test
+  public void testRewriteReferencedDataFile() {
+    Assume.assumeTrue("Delete files are only supported in v2", formatVersion > 1);
+
+    table.newAppend()
+        .appendFile(FILE_A)
+        .commit();
+
+    table.newRowDelta()
+        .addDeletes(FILE_A_DELETES)
+        .commit();
+
+    long snapshotBeforeDeleteRewrite = table.currentSnapshot().snapshotId();
+
+    // simulate rewrite deletes in FILE_A_DELETES to FILE_B_DELETES
+    table.newRewrite()
+        .validateFromSnapshot(snapshotBeforeDeleteRewrite)
+        .validateDataFilesNotRewritten(Sets.newSet(FILE_A.path()))
+        .rewriteFiles(Sets.newSet(), Sets.newSet(FILE_A_DELETES), Sets.newSet(), Sets.newSet(FILE_B_DELETES))
+        .commit();
+
+    long snapshotBeforeRewriteFileA = table.currentSnapshot().snapshotId();
+
+    // rewrite FILE_A as FILE_A2
+    table.newRewrite()
+        .validateFromSnapshot(table.currentSnapshot().snapshotId())
+        .rewriteFiles(Sets.newSet(FILE_A), Sets.newSet(FILE_A2))
+        .commit();
+
+    AssertHelpers.assertThrows("Should fail because a referenced file was rewritten",
+        ValidationException.class, "Cannot commit, missing data files",
+        () -> table.newRewrite()
+            .validateFromSnapshot(snapshotBeforeRewriteFileA)
+            .validateDataFilesNotRewritten(Sets.newSet(FILE_A.path()))
+            .rewriteFiles(Sets.newSet(), Sets.newSet(FILE_B_DELETES), Sets.newSet(), Sets.newSet(FILE_A_DELETES))
+            .apply());
+  }
+
+  @Test
+  public void testOverwriteReferencedDataFile() {
+    Assume.assumeTrue("Delete files are only supported in v2", formatVersion > 1);
+
+    table.newAppend()
+        .appendFile(FILE_A)
+        .commit();
+
+    table.newRowDelta()
+        .addDeletes(FILE_A_DELETES)
+        .commit();
+
+    long snapshotBeforeDeleteRewrite = table.currentSnapshot().snapshotId();
+
+    // simulate rewrite deletes in FILE_A_DELETES to FILE_B_DELETES
+    table.newRewrite()
+        .validateFromSnapshot(snapshotBeforeDeleteRewrite)
+        .validateDataFilesNotRewritten(Sets.newSet(FILE_A.path()))
+        .rewriteFiles(Sets.newSet(), Sets.newSet(FILE_A_DELETES), Sets.newSet(), Sets.newSet(FILE_B_DELETES))
+        .commit();
+
+    long snapshotBeforeOverwriteFileA = table.currentSnapshot().snapshotId();
+
+    // overwrite FILE_A with FILE_A2
+    table.newOverwrite()
+        .deleteFile(FILE_A)
+        .addFile(FILE_A2)
+        .commit();
+
+    // the rewrite succeeds because the overwrite is required to read FILE_A correctly
+    table.newRewrite()
+        .validateFromSnapshot(snapshotBeforeOverwriteFileA)
+        .validateDataFilesNotRewritten(Sets.newSet(FILE_A.path()))
+        .rewriteFiles(Sets.newSet(), Sets.newSet(FILE_B_DELETES), Sets.newSet(), Sets.newSet(FILE_A_DELETES))

Review comment:
       This is the case I was thinking about in my last comment on the other PR. In order for `RewriteAction_1` to be valid, it must reuse the sequence from `FILE_A` for `FILE_B`. Otherwise, the rewrite on its own would have un-deleted a row because `EQ_DELETE_FILE_A` would no longer apply.
   
   The validation in this PR can catch this case because the files referenced by `POS_DELETE_FILE_C` would be passed to the validation. That's `FILE_A` in this case and the commit for `RewriteAction_2` would check that `FILE_A` still exists and would fail. I'm fine merging this PR if you think that this is something that may happen.
   
   But, I think that it is really unlikely that rewrites will alter sequence numbers to avoid applying deletes. That makes little sense because you may as well apply deletes as long as you're rewriting the data. But assuming that you wanted to, this may not even be possible if the files that are rewritten are from different sequence numbers, with different sets of equality delete files that must be applied. I think a far better option is to apply the deletes when rewriting.
   
   I'm fine merging this if you think we need it. I'll remove the draft status so that we can.




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