Remove seemingly unnecessary nullptr check

src/Storages/Kafka/KafkaConsumer2.cpp

@@ -401,15 +401,14 @@ void KafkaConsumer2::commit(const TopicPartition & topic_partition)
 
 ReadBufferPtr KafkaConsumer2::getNextMessage()
 {
-    while (current != messages.end())
+    if (current != messages.end())
     {
         const auto * data = current->get_payload().get_data();
         size_t size = current->get_payload().get_size();
         ++current;
 
-        // TODO(antaljanosbenjamin): When this can be nullptr?
-        if (data)
-            return std::make_shared<ReadBufferFromMemory>(data, size);
+        chassert(data != nullptr);
+        return std::make_shared<ReadBufferFromMemory>(data, size);
     }
 
     return nullptr;
@@ -433,7 +432,11 @@ size_t KafkaConsumer2::filterMessageErrors()
         });
 
     if (skipped)
+    {
         LOG_ERROR(log, "There were {} messages with an error", skipped);
+        // Technically current is invalidated as soon as we erased a single message
+        current = messages.begin();
+    }
 
     return skipped;
 }

tests/integration/test_storage_kafka/test.py

@@ -5444,6 +5444,66 @@ def test_multiple_read_in_materialized_views(kafka_cluster, create_query_generat
         )
 
 
+
+
+@pytest.mark.parametrize(
+    "create_query_generator",
+    [generate_old_create_table_query, generate_new_create_table_query],
+)
+def test_kafka_null_message(kafka_cluster, create_query_generator):
+    topic_name = "null_message"
+
+    instance.query(
+        f"""
+        DROP TABLE IF EXISTS test.null_message_view;
+        DROP TABLE IF EXISTS test.null_message_consumer;
+        DROP TABLE IF EXISTS test.null_message_kafka;
+
+        {create_query_generator("null_message_kafka", "value UInt64", topic_list=topic_name, consumer_group="mv")};
+        CREATE TABLE test.null_message_view (value UInt64)
+            ENGINE = MergeTree()
+            ORDER BY value;
+        CREATE MATERIALIZED VIEW test.null_message_consumer TO test.null_message_view AS
+            SELECT * FROM test.null_message_kafka;
+    """
+    )
+
+    message_key_values = []
+    for i in range(5):
+        # Here the key is key for Kafka message
+        message = json.dumps({"value": i}) if i != 3 else None
+        message_key_values.append({"key": f"{i}".encode(), "message": message})
+
+    producer = get_kafka_producer(
+        kafka_cluster.kafka_port, producer_serializer, 15
+    )
+    for message_kv in message_key_values:
+        producer.send(topic=topic_name, key = message_kv["key"], value=message_kv["message"])
+        producer.flush()
+
+    expected = TSV(
+            """
+0
+1
+2
+4
+"""
+        )
+    with existing_kafka_topic(get_admin_client(kafka_cluster), topic_name):
+        result = instance.query_with_retry(
+            "SELECT * FROM test.null_message_view", check_callback=lambda res: TSV(res) == expected
+        )
+
+        assert expected == TSV(result)
+
+        instance.query(
+            """
+            DROP TABLE test.null_message_consumer;
+            DROP TABLE test.null_message_view;
+            DROP TABLE test.null_message_kafka;
+        """
+        )
+
 if __name__ == "__main__":
     cluster.start()
     input("Cluster created, press any key to destroy...")