rdblue commented on code in PR #7569:
URL: https://github.com/apache/iceberg/pull/7569#discussion_r1199828553


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core/src/main/java/org/apache/iceberg/catalog/TableCommit.java:
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@@ -0,0 +1,33 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.iceberg.catalog;
+
+import java.util.List;
+import org.apache.iceberg.MetadataUpdate;
+import org.apache.iceberg.TableMetadata;
+import org.immutables.value.Value;
+
[email protected]
+public interface TableCommit {
+  TableIdentifier identifier();
+
+  TableMetadata base();

Review Comment:
   As I noted above, I think it would be better to use `requirements` and 
`updates` instead of mixing the updates with a `TableMetadata`.
   
   I think there is a drawback to that approach, though. Any catalog that 
commits using metadata location rather than requirements and updates would be 
harder to update for multi-table transactions because those require the base 
metadata and the new metadata.
   
   Overall, I think I would still prefer the requirements and updates. There 
are a couple of reasons:
   1. Implementations of `TableOperations` almost always refresh immediately 
before attempting a commit anyway. Loading table metadata should not be a 
performance problem.
   2. Some operations don't refresh table metadata before attempting to commit 
because they do not retry. For those cases, we have to address that they are 
not normally retried and use generic retry logic. That's what 
requirements/updates already do.
   
   For a concrete example of point 2 above, consider `UpdateSchema` that does 
not retry. If the table changes concurrently, then the schema update fails. 
That's because the operation doesn't validate that it can still apply the 
schema changes. However, the REST protocol does provide a way to validate a 
schema update can still be applied, by sending an 
`assert-last-assigned-field-id` requirement.
   
   If we were to try to perform a schema update using a multi-table commit 
method, that method doesn't know what is update is happening and will always 
retry. To make that retry safe, we should use the requirements.



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