Core: Add uuid to ViewMetadata

core/src/main/java/org/apache/iceberg/MetadataUpdate.java

@@ -53,6 +53,11 @@ public String uuid() {
     public void applyTo(TableMetadata.Builder metadataBuilder) {
       metadataBuilder.assignUUID(uuid);
     }
+
+    @Override
+    public void applyTo(ViewMetadata.Builder metadataBuilder) {
+      metadataBuilder.assignUUID(uuid);
+    }
   }
 
   class UpgradeFormatVersion implements MetadataUpdate {

core/src/main/java/org/apache/iceberg/view/ViewMetadata.java

@@ -23,6 +23,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.UUID;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 import org.apache.iceberg.MetadataUpdate;
@@ -46,6 +47,8 @@ public interface ViewMetadata extends Serializable {
   int SUPPORTED_VIEW_FORMAT_VERSION = 1;
   int DEFAULT_VIEW_FORMAT_VERSION = 1;
 
+  String uuid();
+
   int formatVersion();
 
   String location();
@@ -141,6 +144,7 @@ class Builder {
     private int formatVersion = DEFAULT_VIEW_FORMAT_VERSION;
     private int currentVersionId;
     private String location;
+    private String uuid;
 
     // internal change tracking
     private Integer lastAddedVersionId = null;
@@ -157,6 +161,7 @@ private Builder() {
       this.history = Lists.newArrayList();
       this.properties = Maps.newHashMap();
       this.changes = Lists.newArrayList();
+      this.uuid = UUID.randomUUID().toString();
     }
 
     private Builder(ViewMetadata base) {
@@ -170,6 +175,7 @@ private Builder(ViewMetadata base) {
       this.formatVersion = base.formatVersion();
       this.currentVersionId = base.currentVersionId();
       this.location = base.location();
+      this.uuid = base.uuid();
     }
 
     public Builder upgradeFormatVersion(int newFormatVersion) {
@@ -353,6 +359,17 @@ public Builder removeProperties(Set<String> propertiesToRemove) {
       return this;
     }
 
+    public ViewMetadata.Builder assignUUID(String newUUID) {
+      Preconditions.checkArgument(newUUID != null, "Cannot set uuid to null");
+
+      if (!newUUID.equals(uuid)) {
+        this.uuid = newUUID;
+        changes.add(new MetadataUpdate.AssignUUID(uuid));
+      }
+
+      return this;
+    }
+
     public ViewMetadata build() {
       Preconditions.checkArgument(null != location, "Invalid location: null");
       Preconditions.checkArgument(versions.size() > 0, "Invalid view: no versions were added");
@@ -386,6 +403,7 @@ public ViewMetadata build() {
       }
 
       return ImmutableViewMetadata.of(
+          uuid,
           formatVersion,
           location,
           schemas,

core/src/main/java/org/apache/iceberg/view/ViewMetadataParser.java

@@ -39,6 +39,7 @@
 
 public class ViewMetadataParser {
 
+  static final String VIEW_UUID = "view-uuid";
   static final String FORMAT_VERSION = "format-version";
   static final String LOCATION = "location";
   static final String CURRENT_VERSION_ID = "current-version-id";
@@ -62,6 +63,7 @@ static void toJson(ViewMetadata metadata, JsonGenerator gen) throws IOException
 
     gen.writeStartObject();
 
+    gen.writeStringField(VIEW_UUID, metadata.uuid());
     gen.writeNumberField(FORMAT_VERSION, metadata.formatVersion());
     gen.writeStringField(LOCATION, metadata.location());
     JsonUtil.writeStringMap(PROPERTIES, metadata.properties(), gen);
@@ -98,6 +100,7 @@ public static ViewMetadata fromJson(JsonNode json) {
     Preconditions.checkArgument(
         json.isObject(), "Cannot parse view metadata from non-object: %s", json);
 
+    String uuid = JsonUtil.getString(VIEW_UUID, json);
     int formatVersion = JsonUtil.getInt(FORMAT_VERSION, json);
     String location = JsonUtil.getString(LOCATION, json);
     Map<String, String> properties = JsonUtil.getStringMap(PROPERTIES, json);
@@ -131,6 +134,7 @@ public static ViewMetadata fromJson(JsonNode json) {
     }
 
     return ImmutableViewMetadata.of(
+        uuid,
         formatVersion,
         location,
         schemas,

core/src/test/java/org/apache/iceberg/view/TestViewMetadata.java

@@ -43,6 +43,8 @@ private ViewVersion newViewVersion(int id, String sql) {
         .defaultCatalog("prod")
         .defaultNamespace(Namespace.of("default"))
         .summary(ImmutableMap.of("operation", "create"))
+        .addRepresentations(
+            ImmutableSQLViewRepresentation.builder().dialect("spark").sql(sql).build())
         .schemaId(1)
         .build();
   }
@@ -101,6 +103,10 @@ public void nullAndMissingFields() {
             () -> ViewMetadata.builder().setLocation("location").setCurrentVersionId(1).build())
         .isInstanceOf(IllegalArgumentException.class)
         .hasMessage("Cannot set current version to unknown version: 1");
+
+    assertThatThrownBy(() -> ViewMetadata.builder().assignUUID(null).build())
+        .isInstanceOf(IllegalArgumentException.class)
+        .hasMessage("Cannot set uuid to null");
   }
 
   @Test
@@ -464,5 +470,17 @@ public void viewMetadataAndMetadataChanges() {
         .asInstanceOf(InstanceOfAssertFactories.type(MetadataUpdate.SetCurrentViewVersion.class))
         .extracting(MetadataUpdate.SetCurrentViewVersion::versionId)
         .isEqualTo(-1);
+
+    ViewMetadata updatedMetadata =
+        ViewMetadata.buildFrom(viewMetadata)
+            .assignUUID("fa6506c3-7681-40c8-86dc-e36561f83385")
+            .build();
+    assertThat(updatedMetadata.changes())
+        .hasSize(1)
+        .first()
+        .isInstanceOf(MetadataUpdate.AssignUUID.class)
+        .asInstanceOf(InstanceOfAssertFactories.type(MetadataUpdate.AssignUUID.class))
+        .extracting(MetadataUpdate.AssignUUID::uuid)
+        .isEqualTo("fa6506c3-7681-40c8-86dc-e36561f83385");
   }
 }

core/src/test/java/org/apache/iceberg/view/TestViewMetadataParser.java

@@ -89,6 +89,7 @@ public void readAndWriteValidViewMetadata() throws Exception {
     String json = readViewMetadataInputFile("org/apache/iceberg/view/ValidViewMetadata.json");
     ViewMetadata expectedViewMetadata =
         ViewMetadata.builder()
+            .assignUUID("fa6506c3-7681-40c8-86dc-e36561f83385")
             .addSchema(TEST_SCHEMA)
             .addVersion(version1)
             .addVersion(version2)

core/src/test/resources/org/apache/iceberg/view/ValidViewMetadata.json

@@ -1,4 +1,5 @@
 {
+  "view-uuid": "fa6506c3-7681-40c8-86dc-e36561f83385",
   "format-version": 1,
   "location": "s3://bucket/test/location",
   "properties": {"some-key": "some-value"},

core/src/test/resources/org/apache/iceberg/view/ViewMetadataInvalidCurrentSchema.json

@@ -1,4 +1,5 @@
 {
+  "view-uuid": "fa6506c3-7681-40c8-86dc-e36561f83385",
   "format-version": 1,
   "location": "s3://bucket/test/location",
   "properties": {"some-key": "some-value"},

core/src/test/resources/org/apache/iceberg/view/ViewMetadataInvalidCurrentVersion.json

@@ -1,4 +1,5 @@
 {
+  "view-uuid": "fa6506c3-7681-40c8-86dc-e36561f83385",
   "format-version": 1,
   "location": "s3://bucket/test/location",
   "properties": {"some-key": "some-value"},

core/src/test/resources/org/apache/iceberg/view/ViewMetadataMissingCurrentVersion.json

@@ -1,4 +1,5 @@
 {
+  "view-uuid": "fa6506c3-7681-40c8-86dc-e36561f83385",
   "format-version": 1,
   "location": "s3://bucket/test/location",
   "properties": {"some-key": "some-value"},

core/src/test/resources/org/apache/iceberg/view/ViewMetadataMissingLocation.json

@@ -1,4 +1,5 @@
 {
+  "view-uuid": "fa6506c3-7681-40c8-86dc-e36561f83385",
   "format-version": 1,
   "properties": {"some-key": "some-value"},
   "current-schema-id": 1,

format/view-spec.md

@@ -58,6 +58,7 @@ The view version metadata file has the following fields:
 
 | Requirement | Field name           | Description |
 |-------------|----------------------|-------------|
+| _required_  | `view-uuid`          | A UUID that identifies the view, generated when the view is created. Implementations must throw an exception if a view's UUID does not match the expected UUID after refreshing metadata |
 | _required_  | `format-version`     | An integer version number for the view format; must be 1 |
 | _required_  | `location`           | The view's base location; used to create metadata file locations |
 | _required_  | `schemas`            | A list of known schemas |
@@ -192,6 +193,7 @@ s3://bucket/warehouse/default.db/event_agg/metadata/00001-(uuid).metadata.json
 ```
 ```
 {
+  "view-uuid": "fa6506c3-7681-40c8-86dc-e36561f83385",
   "format-version" : 1,
   "location" : "s3://bucket/warehouse/default.db/event_agg",
   "current-version-id" : 1,
@@ -259,6 +261,7 @@ s3://bucket/warehouse/default.db/event_agg/metadata/00002-(uuid).metadata.json
 ```
 ```
 {
+  "view-uuid": "fa6506c3-7681-40c8-86dc-e36561f83385",
   "format-version" : 1,
   "location" : "s3://bucket/warehouse/default.db/event_agg",
   "current-version-id" : 1,