Core: add labels to the load table/view read path

core/src/main/java/org/apache/iceberg/rest/labels/FieldLabels.java

@@ -0,0 +1,37 @@
+/*
+ * 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.rest.labels;
+
+import java.util.Map;
+import org.apache.iceberg.relocated.com.google.common.base.Preconditions;
+import org.immutables.value.Value;
+
+/** Labels attached to a single field, identified by its field id. See {@link Labels}. */
+@Value.Immutable
+public interface FieldLabels {
+  int fieldId();
+
+  Map<String, String> labels();
+
+  @Value.Check
+  default void validate() {
+    Preconditions.checkArgument(fieldId() >= 1, "Invalid field id: must be >= 1");
+    Preconditions.checkArgument(!labels().isEmpty(), "Invalid labels: must be non-empty");
+  }
+}

core/src/main/java/org/apache/iceberg/rest/labels/FieldLabelsParser.java

@@ -0,0 +1,64 @@
+/*
+ * 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.rest.labels;
+
+import com.fasterxml.jackson.core.JsonGenerator;
+import com.fasterxml.jackson.databind.JsonNode;
+import java.io.IOException;
+import org.apache.iceberg.relocated.com.google.common.base.Preconditions;
+import org.apache.iceberg.util.JsonUtil;
+
+public class FieldLabelsParser {
+  private static final String FIELD_ID = "field-id";
+  private static final String LABELS = "labels";
+
+  private FieldLabelsParser() {}
+
+  public static String toJson(FieldLabels fieldLabels) {
+    return toJson(fieldLabels, false);
+  }
+
+  public static String toJson(FieldLabels fieldLabels, boolean pretty) {
+    return JsonUtil.generate(gen -> toJson(fieldLabels, gen), pretty);
+  }
+
+  public static void toJson(FieldLabels fieldLabels, JsonGenerator gen) throws IOException {
+    Preconditions.checkArgument(null != fieldLabels, "Invalid field labels: null");
+
+    gen.writeStartObject();
+
+    gen.writeNumberField(FIELD_ID, fieldLabels.fieldId());
+    JsonUtil.writeStringMap(LABELS, fieldLabels.labels(), gen);
+
+    gen.writeEndObject();
+  }
+
+  public static FieldLabels fromJson(String json) {
+    return JsonUtil.parse(json, FieldLabelsParser::fromJson);
+  }
+
+  public static FieldLabels fromJson(JsonNode json) {
+    Preconditions.checkArgument(null != json, "Cannot parse field labels from null object");
+
+    return ImmutableFieldLabels.builder()
+        .fieldId(JsonUtil.getInt(FIELD_ID, json))
+        .labels(JsonUtil.getStringMap(LABELS, json))
+        .build();
+  }
+}

core/src/main/java/org/apache/iceberg/rest/labels/Labels.java

@@ -0,0 +1,45 @@
+/*
+ * 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.rest.labels;
+
+import java.util.List;
+import java.util.Map;
+import org.immutables.value.Value;
+
+/** Optional catalog-provided labels returned on a load response. */
+@Value.Immutable
+public interface Labels {
+  Labels EMPTY = ImmutableLabels.builder().build();
+
+  /** Object-level labels. */
+  Map<String, String> object();
+
+  /** Field-level labels, keyed by field id. */
+  List<FieldLabels> fields();
+
+  /** Returns true when there are neither object-level nor field-level labels. */
+  default boolean isEmpty() {
+    return object().isEmpty() && fields().isEmpty();
+  }
+
+  /** Returns a shared empty instance. */
+  static Labels empty() {
+    return EMPTY;
+  }
+}

core/src/main/java/org/apache/iceberg/rest/labels/LabelsParser.java

@@ -0,0 +1,81 @@
+/*
+ * 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.rest.labels;
+
+import com.fasterxml.jackson.core.JsonGenerator;
+import com.fasterxml.jackson.databind.JsonNode;
+import java.io.IOException;
+import org.apache.iceberg.relocated.com.google.common.base.Preconditions;
+import org.apache.iceberg.util.JsonUtil;
+
+public class LabelsParser {
+  private static final String OBJECT = "object";
+  private static final String FIELDS = "fields";
+
+  private LabelsParser() {}
+
+  public static String toJson(Labels labels) {
+    return toJson(labels, false);
+  }
+
+  public static String toJson(Labels labels, boolean pretty) {
+    return JsonUtil.generate(gen -> toJson(labels, gen), pretty);
+  }
+
+  public static void toJson(Labels labels, JsonGenerator gen) throws IOException {
+    Preconditions.checkArgument(null != labels, "Invalid labels: null");
+
+    gen.writeStartObject();
+
+    if (!labels.object().isEmpty()) {
+      JsonUtil.writeStringMap(OBJECT, labels.object(), gen);
+    }
+
+    if (!labels.fields().isEmpty()) {
+      gen.writeArrayFieldStart(FIELDS);
+      for (FieldLabels fieldLabels : labels.fields()) {
+        FieldLabelsParser.toJson(fieldLabels, gen);
+      }
+
+      gen.writeEndArray();
+    }
+
+    gen.writeEndObject();
+  }
+
+  public static Labels fromJson(String json) {
+    return JsonUtil.parse(json, LabelsParser::fromJson);
+  }
+
+  public static Labels fromJson(JsonNode json) {
+    Preconditions.checkArgument(null != json, "Cannot parse labels from null object");
+
+    ImmutableLabels.Builder builder = ImmutableLabels.builder();
+
+    if (json.hasNonNull(OBJECT)) {
+      builder.object(JsonUtil.getStringMap(OBJECT, json));
+    }
+
+    if (json.hasNonNull(FIELDS)) {
+      builder.fields(JsonUtil.getObjectList(FIELDS, json, FieldLabelsParser::fromJson));
+    }
+
+    return builder.build();
+  }
+}

core/src/main/java/org/apache/iceberg/rest/responses/LoadTableResponse.java

@@ -29,6 +29,7 @@
 import org.apache.iceberg.relocated.com.google.common.collect.Maps;
 import org.apache.iceberg.rest.RESTResponse;
 import org.apache.iceberg.rest.credentials.Credential;
+import org.apache.iceberg.rest.labels.Labels;
 
 /**
  * A REST response that is used when a table is successfully loaded.
@@ -45,6 +46,7 @@ public class LoadTableResponse implements RESTResponse {
   private Map<String, String> config;
   private TableMetadata metadataWithLocation;
   private List<Credential> credentials;
+  private Labels labels;
 
   public LoadTableResponse() {
     // Required for Jackson deserialization
@@ -54,11 +56,13 @@ private LoadTableResponse(
       String metadataLocation,
       TableMetadata metadata,
       Map<String, String> config,
-      List<Credential> credentials) {
+      List<Credential> credentials,
+      Labels labels) {
     this.metadataLocation = metadataLocation;
     this.metadata = metadata;
     this.config = config;
     this.credentials = credentials;
+    this.labels = labels;
   }
 
   @Override
@@ -87,12 +91,18 @@ public List<Credential> credentials() {
     return credentials != null ? credentials : ImmutableList.of();
   }
 
+  /** Catalog-provided labels, or an empty instance when the response carries no labels. */
+  public Labels labels() {
+    return labels != null ? labels : Labels.empty();
+  }
+
   @Override
   public String toString() {
     return MoreObjects.toStringHelper(this)
         .add("metadataLocation", metadataLocation)
         .add("metadata", metadata)
         .add("config", config)
+        .add("labels", labels)
         .toString();
   }
 
@@ -105,6 +115,7 @@ public static class Builder {
     private TableMetadata metadata;
     private final Map<String, String> config = Maps.newHashMap();
     private final List<Credential> credentials = Lists.newArrayList();
+    private Labels labels;
 
     private Builder() {}
 
@@ -134,9 +145,14 @@ public Builder addAllCredentials(List<Credential> credentialsToAdd) {
       return this;
     }
 
+    public Builder withLabels(Labels tableLabels) {
+      this.labels = tableLabels;
+      return this;
+    }
+
     public LoadTableResponse build() {
       Preconditions.checkNotNull(metadata, "Invalid metadata: null");
-      return new LoadTableResponse(metadataLocation, metadata, config, credentials);
+      return new LoadTableResponse(metadataLocation, metadata, config, credentials, labels);
     }
   }
 }

core/src/main/java/org/apache/iceberg/rest/responses/LoadTableResponseParser.java

@@ -26,6 +26,7 @@
 import org.apache.iceberg.relocated.com.google.common.base.Preconditions;
 import org.apache.iceberg.rest.credentials.Credential;
 import org.apache.iceberg.rest.credentials.CredentialParser;
+import org.apache.iceberg.rest.labels.LabelsParser;
 import org.apache.iceberg.util.JsonUtil;
 
 public class LoadTableResponseParser {
@@ -34,6 +35,7 @@ public class LoadTableResponseParser {
   private static final String METADATA = "metadata";
   private static final String CONFIG = "config";
   private static final String STORAGE_CREDENTIALS = "storage-credentials";
+  private static final String LABELS = "labels";
 
   private LoadTableResponseParser() {}
 
@@ -70,6 +72,11 @@ public static void toJson(LoadTableResponse response, JsonGenerator gen) throws
       gen.writeEndArray();
     }
 
+    if (!response.labels().isEmpty()) {
+      gen.writeFieldName(LABELS);
+      LabelsParser.toJson(response.labels(), gen);
+    }
+
     gen.writeEndObject();
   }
 
@@ -101,6 +108,10 @@ public static LoadTableResponse fromJson(JsonNode json) {
       builder.addAllCredentials(LoadCredentialsResponseParser.fromJson(json).credentials());
     }
 
+    if (json.hasNonNull(LABELS)) {
+      builder.withLabels(LabelsParser.fromJson(JsonUtil.get(LABELS, json)));
+    }
+
     return builder.build();
   }
 }

core/src/main/java/org/apache/iceberg/rest/responses/LoadViewResponse.java

@@ -20,6 +20,7 @@
 
 import java.util.Map;
 import org.apache.iceberg.rest.RESTResponse;
+import org.apache.iceberg.rest.labels.Labels;
 import org.apache.iceberg.view.ViewMetadata;
 import org.immutables.value.Value;
 
@@ -31,6 +32,12 @@ public interface LoadViewResponse extends RESTResponse {
 
   Map<String, String> config();
 
+  /** Catalog-provided labels, or an empty instance when the response carries no labels. */
+  @Value.Default
+  default Labels labels() {
+    return Labels.empty();
+  }
+
   @Override
   default void validate() {
     // nothing to validate as it's not possible to create an invalid instance