[Kernel] Add Domain Metadata support to Delta Kernel (delta-io#3835)

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#### Which Delta project/connector is this regarding?
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- [ ] Spark
- [ ] Standalone
- [ ] Flink
- [x] Kernel
- [ ] Other (fill in here)

## Description

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- Describe what this PR changes.
- Describe why we need the change.
 
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This PR adds support for domain metadata to Delta Kernel as described in
the [Delta
Protocal](https://github.com/delta-io/delta/blob/master/PROTOCOL.md#domain-metadata).

In particular, it adds the following to Delta Kernel:
- `DomainMetadata` Class
- Used to represent a [domain metadata
action](https://github.com/delta-io/delta/blob/master/PROTOCOL.md#domain-metadata)
as described in the Delta Protocol.
- Includes necessary utility functions, such as creating a
`DomainMetadata` instance from `Row`/`ColumnVector` and creating a
action `Row` from a `DomainMetadata` instance for committing.

- Transaction Support
- Checks for duplicate domain metadata and protocol support prior to
committing them.
- Adds an internal `addDomainMetadata` API to `TransactionImpl` for
testing purposes. In real scenarios, domain metadata will be constructed
by feature-specific code within `TransactionImpl`. A future PR
introducing Row Tracking will provide a concrete example of domain
metadata usage in practice.
  
- Checkpointing
  - Domain metadata is maintained during checkpointing.
 
- Log Replay.
- Currently, domain metadata is lazily load in a separate pass of reply
when requested.
- We might want to improve this in the future by caching domain metadata
during the initial Protocol & Metadata replay.
  
- Conflict Resolution.
- Two overlapping transactions conflict if they include domain metadata
actions for the same metadata domain.
- Future features can implement custom conflict resolution logic as
needed.
  
- Adds `domainMetadata` to `SUPPORTED_WRITER_FEATURES`

## How was this patch tested?

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Added tests covering operations involving DomainMetadata in
`DomainMetadataSuite`.
- Unit tests for committing, log replaying, checkpointing, and conflict
resolution related to domain metadata. Negative tests for missing writer
feature in the protocol and duplicate domain metadata actions.
- Integration tests where a table with domain metadata is write by Spark
and read by Kernel, and vice versa.

## Does this PR introduce _any_ user-facing changes?

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If yes, please clarify the previous behavior and the change this PR
proposes - provide the console output, description and/or an example to
show the behavior difference if possible.
If possible, please also clarify if this is a user-facing change
compared to the released Delta Lake versions or within the unreleased
branches such as master.
If no, write 'No'.
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 No.
Domain metadata is currently intended for internal use by kernel
developers to support specific table features. We don't plan to allow
users to create their own domain metadata in the near future. So this PR
only involves changes to internal APIs with no additions/modifications
to public APIs.

---------

Co-authored-by: Johan Lasperas <[email protected]>

Author: qiyuandong-db

kernel/kernel-api/src/main/java/io/delta/kernel/internal/DeltaErrors.java

@@ -18,6 +18,7 @@
 import static java.lang.String.format;
 
 import io.delta.kernel.exceptions.*;
+import io.delta.kernel.internal.actions.DomainMetadata;
 import io.delta.kernel.types.DataType;
 import io.delta.kernel.types.StructType;
 import io.delta.kernel.utils.DataFileStatus;
@@ -274,6 +275,24 @@ public static KernelException invalidConfigurationValueException(
     return new InvalidConfigurationValueException(key, value, helpMessage);
   }
 
+  public static KernelException domainMetadataUnsupported() {
+    String message =
+        "Cannot commit DomainMetadata action(s) because the feature 'domainMetadata' "
+            + "is not supported on this table.";
+    return new KernelException(message);
+  }
+
+  public static ConcurrentWriteException concurrentDomainMetadataAction(
+      DomainMetadata domainMetadataAttempt, DomainMetadata winningDomainMetadata) {
+    String message =
+        String.format(
+            "A concurrent writer added a domainMetadata action for the same domain: %s. "
+                + "No domain-specific conflict resolution is available for this domain. "
+                + "Attempted domainMetadata: %s. Winning domainMetadata: %s",
+            domainMetadataAttempt.getDomain(), domainMetadataAttempt, winningDomainMetadata);
+    return new ConcurrentWriteException(message);
+  }
+
   /* ------------------------ HELPER METHODS ----------------------------- */
   private static String formatTimestamp(long millisSinceEpochUTC) {
     return new Timestamp(millisSinceEpochUTC).toInstant().toString();

kernel/kernel-api/src/main/java/io/delta/kernel/internal/SnapshotImpl.java

@@ -23,6 +23,7 @@
 import io.delta.kernel.engine.CommitCoordinatorClientHandler;
 import io.delta.kernel.engine.Engine;
 import io.delta.kernel.internal.actions.CommitInfo;
+import io.delta.kernel.internal.actions.DomainMetadata;
 import io.delta.kernel.internal.actions.Metadata;
 import io.delta.kernel.internal.actions.Protocol;
 import io.delta.kernel.internal.fs.Path;
@@ -31,6 +32,7 @@
 import io.delta.kernel.internal.snapshot.LogSegment;
 import io.delta.kernel.internal.snapshot.TableCommitCoordinatorClientHandler;
 import io.delta.kernel.types.StructType;
+import java.util.Map;
 import java.util.Optional;
 
 /** Implementation of {@link Snapshot}. */
@@ -83,6 +85,17 @@ public Protocol getProtocol() {
     return protocol;
   }
 
+  /**
+   * Get the domain metadata map from the log replay, which lazily loads and replays a history of
+   * domain metadata actions, resolving them to produce the current state of the domain metadata.
+   *
+   * @return A map where the keys are domain names and the values are {@link DomainMetadata}
+   *     objects.
+   */
+  public Map<String, DomainMetadata> getDomainMetadataMap() {
+    return logReplay.getDomainMetadataMap();
+  }
+
   public CreateCheckpointIterator getCreateCheckpointIterator(Engine engine) {
     long minFileRetentionTimestampMillis =
         System.currentTimeMillis() - TOMBSTONE_RETENTION.fromMetadata(metadata);

kernel/kernel-api/src/main/java/io/delta/kernel/internal/TableFeatures.java

@@ -39,6 +39,7 @@ public class TableFeatures {
               add("columnMapping");
               add("typeWidening-preview");
               add("typeWidening");
+              add(DOMAIN_METADATA_FEATURE_NAME);
             }
           });
 
@@ -57,6 +58,12 @@ public class TableFeatures {
             }
           });
 
+  /** The feature name for domain metadata. */
+  public static final String DOMAIN_METADATA_FEATURE_NAME = "domainMetadata";
+
+  /** The minimum writer version required to support table features. */
+  public static final int TABLE_FEATURES_MIN_WRITER_VERSION = 7;
+
   ////////////////////
   // Helper Methods //
   ////////////////////
@@ -93,7 +100,7 @@ public static void validateReadSupportedTable(
    *   <li>protocol writer version 1.
    *   <li>protocol writer version 2 only with appendOnly feature enabled.
    *   <li>protocol writer version 7 with {@code appendOnly}, {@code inCommitTimestamp}, {@code
-   *       columnMapping}, {@code typeWidening} feature enabled.
+   *       columnMapping}, {@code typeWidening}, {@code domainMetadata} feature enabled.
    * </ul>
    *
    * @param protocol Table protocol
@@ -125,20 +132,8 @@ public static void validateWriteSupportedTable(
         throw unsupportedWriterProtocol(tablePath, minWriterVersion);
       case 7:
         for (String writerFeature : protocol.getWriterFeatures()) {
-          switch (writerFeature) {
-              // Only supported writer features as of today in Kernel
-            case "appendOnly":
-              break;
-            case "inCommitTimestamp":
-              break;
-            case "columnMapping":
-              break;
-            case "typeWidening-preview":
-              break;
-            case "typeWidening":
-              break;
-            default:
-              throw unsupportedWriterFeature(tablePath, writerFeature);
+          if (!SUPPORTED_WRITER_FEATURES.contains(writerFeature)) {
+            throw unsupportedWriterFeature(tablePath, writerFeature);
           }
         }
         break;
@@ -187,6 +182,21 @@ public static Set<String> extractAutomaticallyEnabledWriterFeatures(
         .collect(Collectors.toSet());
   }
 
+  /**
+   * Checks if the table protocol supports the "domainMetadata" writer feature.
+   *
+   * @param protocol the protocol to check
+   * @return true if the "domainMetadata" feature is supported, false otherwise
+   */
+  public static boolean isDomainMetadataSupported(Protocol protocol) {
+    List<String> writerFeatures = protocol.getWriterFeatures();
+    if (writerFeatures == null) {
+      return false;
+    }
+    return writerFeatures.contains(DOMAIN_METADATA_FEATURE_NAME)
+        && protocol.getMinWriterVersion() >= TABLE_FEATURES_MIN_WRITER_VERSION;
+  }
+
   /**
    * Get the minimum reader version required for a feature.
    *

kernel/kernel-api/src/main/java/io/delta/kernel/internal/TransactionImpl.java

@@ -32,11 +32,7 @@
 import io.delta.kernel.internal.fs.Path;
 import io.delta.kernel.internal.replay.ConflictChecker;
 import io.delta.kernel.internal.replay.ConflictChecker.TransactionRebaseState;
-import io.delta.kernel.internal.util.Clock;
-import io.delta.kernel.internal.util.ColumnMapping;
-import io.delta.kernel.internal.util.FileNames;
-import io.delta.kernel.internal.util.InCommitTimestampUtils;
-import io.delta.kernel.internal.util.VectorUtils;
+import io.delta.kernel.internal.util.*;
 import io.delta.kernel.types.StructType;
 import io.delta.kernel.utils.CloseableIterable;
 import io.delta.kernel.utils.CloseableIterator;
@@ -73,6 +69,7 @@ public class TransactionImpl implements Transaction {
   private final Optional<SetTransaction> setTxnOpt;
   private final boolean shouldUpdateProtocol;
   private final Clock clock;
+  private final List<DomainMetadata> domainMetadatas = new ArrayList<>();
   private Metadata metadata;
   private boolean shouldUpdateMetadata;
 
@@ -120,6 +117,23 @@ public StructType getSchema(Engine engine) {
     return readSnapshot.getSchema(engine);
   }
 
+  public Optional<SetTransaction> getSetTxnOpt() {
+    return setTxnOpt;
+  }
+
+  /**
+   * Internal API to add domain metadata actions for this transaction. Visible for testing.
+   *
+   * @param domainMetadatas List of domain metadata to be added to the transaction.
+   */
+  public void addDomainMetadatas(List<DomainMetadata> domainMetadatas) {
+    this.domainMetadatas.addAll(domainMetadatas);
+  }
+
+  public List<DomainMetadata> getDomainMetadatas() {
+    return domainMetadatas;
+  }
+
   @Override
   public TransactionCommitResult commit(Engine engine, CloseableIterable<Row> dataActions)
       throws ConcurrentWriteException {
@@ -221,6 +235,12 @@ private TransactionCommitResult doCommit(
     }
     setTxnOpt.ifPresent(setTxn -> metadataActions.add(createTxnSingleAction(setTxn.toRow())));
 
+    // Check for duplicate domain metadata and if the protocol supports
+    DomainMetadataUtils.validateDomainMetadatas(domainMetadatas, protocol);
+
+    domainMetadatas.forEach(
+        dm -> metadataActions.add(createDomainMetadataSingleAction(dm.toRow())));
+
     try (CloseableIterator<Row> stageDataIter = dataActions.iterator()) {
       // Create a new CloseableIterator that will return the metadata actions followed by the
       // data actions.
@@ -265,10 +285,6 @@ public boolean isBlindAppend() {
     return true;
   }
 
-  public Optional<SetTransaction> getSetTxnOpt() {
-    return setTxnOpt;
-  }
-
   /**
    * Generates a timestamp which is greater than the commit timestamp of the readSnapshot. This can
    * result in an additional file read and that this will only happen if ICT is enabled.

kernel/kernel-api/src/main/java/io/delta/kernel/internal/actions/DomainMetadata.java

@@ -0,0 +1,141 @@
+/*
+ * Copyright (2024) The Delta Lake Project Authors.
+ *
+ * Licensed 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 io.delta.kernel.internal.actions;
+
+import static io.delta.kernel.internal.util.InternalUtils.requireNonNull;
+import static io.delta.kernel.internal.util.Preconditions.checkArgument;
+import static java.util.Objects.requireNonNull;
+
+import io.delta.kernel.data.ColumnVector;
+import io.delta.kernel.data.Row;
+import io.delta.kernel.internal.data.GenericRow;
+import io.delta.kernel.types.BooleanType;
+import io.delta.kernel.types.StringType;
+import io.delta.kernel.types.StructType;
+import java.util.HashMap;
+import java.util.Map;
+
+/** Delta log action representing an `DomainMetadata` action */
+public class DomainMetadata {
+  /** Full schema of the {@link DomainMetadata} action in the Delta Log. */
+  public static final StructType FULL_SCHEMA =
+      new StructType()
+          .add("domain", StringType.STRING, false /* nullable */)
+          .add("configuration", StringType.STRING, false /* nullable */)
+          .add("removed", BooleanType.BOOLEAN, false /* nullable */);
+
+  public static DomainMetadata fromColumnVector(ColumnVector vector, int rowId) {
+    if (vector.isNullAt(rowId)) {
+      return null;
+    }
+    return new DomainMetadata(
+        requireNonNull(vector.getChild(0), rowId, "domain").getString(rowId),
+        requireNonNull(vector.getChild(1), rowId, "configuration").getString(rowId),
+        requireNonNull(vector.getChild(2), rowId, "removed").getBoolean(rowId));
+  }
+
+  /**
+   * Creates a {@link DomainMetadata} instance from a Row with the schema being {@link
+   * DomainMetadata#FULL_SCHEMA}.
+   *
+   * @param row the Row object containing the DomainMetadata action
+   * @return a DomainMetadata instance or null if the row is null
+   * @throws IllegalArgumentException if the schema of the row does not match {@link
+   *     DomainMetadata#FULL_SCHEMA}
+   */
+  public static DomainMetadata fromRow(Row row) {
+    if (row == null) {
+      return null;
+    }
+    checkArgument(
+        row.getSchema().equals(FULL_SCHEMA),
+        "Expected schema: %s, found: %s",
+        FULL_SCHEMA,
+        row.getSchema());
+    return new DomainMetadata(
+        requireNonNull(row, 0, "domain").getString(0),
+        requireNonNull(row, 1, "configuration").getString(1),
+        requireNonNull(row, 2, "removed").getBoolean(2));
+  }
+
+  private final String domain;
+  private final String configuration;
+  private final boolean removed;
+
+  /**
+   * The domain metadata action contains a configuration string for a named metadata domain. Two
+   * overlapping transactions conflict if they both contain a domain metadata action for the same
+   * metadata domain. Per-domain conflict resolution logic can be implemented.
+   *
+   * @param domain A string used to identify a specific domain.
+   * @param configuration A string containing configuration for the metadata domain.
+   * @param removed If it is true it serves as a tombstone to logically delete a {@link
+   *     DomainMetadata} action.
+   */
+  public DomainMetadata(String domain, String configuration, boolean removed) {
+    this.domain = requireNonNull(domain, "domain is null");
+    this.configuration = requireNonNull(configuration, "configuration is null");
+    this.removed = removed;
+  }
+
+  public String getDomain() {
+    return domain;
+  }
+
+  public String getConfiguration() {
+    return configuration;
+  }
+
+  public boolean isRemoved() {
+    return removed;
+  }
+
+  /**
+   * Encode as a {@link Row} object with the schema {@link DomainMetadata#FULL_SCHEMA}.
+   *
+   * @return {@link Row} object with the schema {@link DomainMetadata#FULL_SCHEMA}
+   */
+  public Row toRow() {
+    Map<Integer, Object> domainMetadataMap = new HashMap<>();
+    domainMetadataMap.put(0, domain);
+    domainMetadataMap.put(1, configuration);
+    domainMetadataMap.put(2, removed);
+
+    return new GenericRow(DomainMetadata.FULL_SCHEMA, domainMetadataMap);
+  }
+
+  @Override
+  public String toString() {
+    return String.format(
+        "DomainMetadata{domain='%s', configuration='%s', removed='%s'}",
+        domain, configuration, removed);
+  }
+
+  @Override
+  public boolean equals(Object obj) {
+    if (this == obj) return true;
+    if (obj == null || getClass() != obj.getClass()) return false;
+    DomainMetadata that = (DomainMetadata) obj;
+    return removed == that.removed
+        && domain.equals(that.domain)
+        && configuration.equals(that.configuration);
+  }
+
+  @Override
+  public int hashCode() {
+    return java.util.Objects.hash(domain, configuration, removed);
+  }
+}