write-command: use legacy op with unacknowledged write if server supports it

This should be faster than submitting write commands.

Author: Christian Hergert

src/mongoc/mongoc-write-command.c

@@ -455,6 +455,19 @@ _mongoc_write_command_delete (mongoc_write_command_t       *command,
    BSON_ASSERT (hint);
    BSON_ASSERT (collection);
 
+   /*
+    * If we have an unacknowledged write and the server supports the legacy
+    * opcodes, then submit the legacy opcode so we don't need to wait for
+    * a response from the server.
+    */
+   if ((client->cluster.nodes [hint - 1].min_wire_version == 0) &&
+       !_mongoc_write_concern_has_gle (write_concern)) {
+      _mongoc_write_command_delete_legacy (command, client, hint, database,
+                                           collection, write_concern, result,
+                                           error);
+      EXIT;
+   }
+
    BSON_APPEND_UTF8 (&cmd, "delete", collection);
    BSON_APPEND_DOCUMENT (&cmd, "writeConcern",
                          WRITE_CONCERN_DOC (write_concern));
@@ -515,6 +528,19 @@ _mongoc_write_command_insert (mongoc_write_command_t       *command,
    BSON_ASSERT (hint);
    BSON_ASSERT (collection);
 
+   /*
+    * If we have an unacknowledged write and the server supports the legacy
+    * opcodes, then submit the legacy opcode so we don't need to wait for
+    * a response from the server.
+    */
+   if ((client->cluster.nodes [hint - 1].min_wire_version == 0) &&
+       !_mongoc_write_concern_has_gle (write_concern)) {
+      _mongoc_write_command_insert_legacy (command, client, hint, database,
+                                           collection, write_concern, result,
+                                           error);
+      EXIT;
+   }
+
    if (!command->u.insert.n_documents ||
        !bson_iter_init (&iter, command->u.insert.documents) ||
        !bson_iter_next (&iter)) {
@@ -618,6 +644,19 @@ _mongoc_write_command_update (mongoc_write_command_t       *command,
    BSON_ASSERT (hint);
    BSON_ASSERT (collection);
 
+   /*
+    * If we have an unacknowledged write and the server supports the legacy
+    * opcodes, then submit the legacy opcode so we don't need to wait for
+    * a response from the server.
+    */
+   if ((client->cluster.nodes [hint - 1].min_wire_version == 0) &&
+       !_mongoc_write_concern_has_gle (write_concern)) {
+      _mongoc_write_command_update_legacy (command, client, hint, database,
+                                           collection, write_concern, result,
+                                           error);
+      EXIT;
+   }
+
    BSON_APPEND_UTF8 (&cmd, "update", collection);
    BSON_APPEND_DOCUMENT (&cmd, "writeConcern",
                          WRITE_CONCERN_DOC (write_concern));