[FLINK-32008][protobuf] Ensure bulk persistence is not supported

flink-formats/flink-protobuf/pom.xml

@@ -56,6 +56,16 @@ under the License.
 			<scope>provided</scope>
 		</dependency>
 
+		<!-- Filesystem connector is only present to ensure bulk files are not supported -->
+
+		<dependency>
+			<groupId>org.apache.flink</groupId>
+			<artifactId>flink-connector-files</artifactId>
+			<version>${project.version}</version>
+			<scope>provided</scope>
+			<optional>true</optional>
+		</dependency>
+
 		<dependency>
 			<groupId>com.google.protobuf</groupId>
 			<artifactId>protobuf-java</artifactId>

flink-formats/flink-protobuf/src/main/java/org/apache/flink/formats/protobuf/PbFileFormatFactory.java

@@ -0,0 +1,83 @@
+/*
+ * 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.flink.formats.protobuf;
+
+import org.apache.flink.annotation.Internal;
+import org.apache.flink.api.common.serialization.BulkWriter.Factory;
+import org.apache.flink.configuration.ConfigOption;
+import org.apache.flink.configuration.ReadableConfig;
+import org.apache.flink.connector.file.table.factories.BulkReaderFormatFactory;
+import org.apache.flink.connector.file.table.factories.BulkWriterFormatFactory;
+import org.apache.flink.connector.file.table.format.BulkDecodingFormat;
+import org.apache.flink.table.api.ValidationException;
+import org.apache.flink.table.connector.format.EncodingFormat;
+import org.apache.flink.table.data.RowData;
+import org.apache.flink.table.factories.DynamicTableFactory;
+
+import java.util.Collections;
+import java.util.Set;
+
+/**
+ * Throw a {@link ValidationException} when using Protobuf format factory for file system.
+ *
+ * <p>In practice, there is <a href="https://protobuf.dev/programming-guides/techniques/#streaming">
+ * no standard</a> for storing bulk protobuf messages. This factory is present to prevent falling
+ * back to the {@link org.apache.flink.connector.file.table.DeserializationSchemaAdapter}, a
+ * line-based format which could silently succeed but write unrecoverable data to disk.
+ *
+ * <p>If your use case requires storing bulk protobuf messages on disk, the parquet file format
+ * might be the appropriate container and has an API for mapping records to protobuf messages.
+ */
+@Internal
+public class PbFileFormatFactory implements BulkReaderFormatFactory, BulkWriterFormatFactory {
+
+    @Override
+    public String factoryIdentifier() {
+        return PbFormatFactory.IDENTIFIER;
+    }
+
+    @Override
+    public Set<ConfigOption<?>> requiredOptions() {
+        return Collections.emptySet();
+    }
+
+    @Override
+    public Set<ConfigOption<?>> optionalOptions() {
+        return Collections.emptySet();
+    }
+
+    @Override
+    public Set<ConfigOption<?>> forwardOptions() {
+        return Collections.emptySet();
+    }
+
+    @Override
+    public BulkDecodingFormat<RowData> createDecodingFormat(
+            DynamicTableFactory.Context context, ReadableConfig formatOptions) {
+        throw new ValidationException(
+                "The 'protobuf' format is not supported for the 'filesystem' connector.");
+    }
+
+    @Override
+    public EncodingFormat<Factory<RowData>> createEncodingFormat(
+            DynamicTableFactory.Context context, ReadableConfig formatOptions) {
+        throw new ValidationException(
+                "The 'protobuf' format is not supported for the 'filesystem' connector.");
+    }
+}

flink-formats/flink-protobuf/src/main/resources/META-INF/services/org.apache.flink.table.factories.Factory

@@ -13,3 +13,4 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 org.apache.flink.formats.protobuf.PbFormatFactory
+org.apache.flink.formats.protobuf.PbFileFormatFactory

flink-formats/flink-protobuf/src/test/java/org/apache/flink/formats/protobuf/ProtobufSQLITCaseTest.java

@@ -22,6 +22,7 @@
 import org.apache.flink.formats.protobuf.testproto.MapTest;
 import org.apache.flink.formats.protobuf.testproto.Pb3Test;
 import org.apache.flink.table.api.TableResult;
+import org.apache.flink.table.api.ValidationException;
 import org.apache.flink.table.planner.runtime.utils.BatchTestBase;
 import org.apache.flink.types.Row;
 import org.apache.flink.util.CloseableIterator;
@@ -31,6 +32,8 @@
 import java.util.Map;
 import java.util.concurrent.ExecutionException;
 
+import static org.apache.flink.core.testutils.FlinkAssertions.anyCauseMatches;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNull;
@@ -328,4 +331,33 @@ public void testSinkWithNullLiteralWithEscape() throws Exception {
         MapTest.InnerMessageTest innerMessageTest = mapTest.getMap2Map().get("b");
         assertEquals(MapTest.InnerMessageTest.getDefaultInstance(), innerMessageTest);
     }
+
+    @Test
+    public void testUnsupportedBulkFilesystemSink() {
+        env().setParallelism(1);
+        String sql =
+                "create table bigdata_sink ( "
+                        + "	a int, "
+                        + "	map1 map<string,string>,"
+                        + " map2 map<string, row<a int, b bigint>>"
+                        + ")  with ("
+                        + "	'connector' = 'filesystem', "
+                        + "	'path' = '/tmp/unused', "
+                        + "	'format' = 'protobuf', "
+                        + " 'protobuf.message-class-name' = 'org.apache.flink.formats.protobuf.testproto.MapTest'"
+                        + ")";
+        tEnv().executeSql(sql);
+
+        assertThatThrownBy(
+                        () -> {
+                            TableResult tableResult =
+                                    tEnv().executeSql(
+                                                    "insert into bigdata_sink select 1, map['a', 'b', 'c', 'd'], map['f', row(1,cast(2 as bigint))] ");
+                            tableResult.await();
+                        })
+                .satisfies(
+                        anyCauseMatches(
+                                ValidationException.class,
+                                "The 'protobuf' format is not supported for the 'filesystem' connector."));
+    }
 }