Allow write/read unnamed tuple as nested Message in Protobuf format

src/Formats/ProtobufSerializer.cpp

@@ -3453,15 +3453,35 @@ namespace
                     const auto & tuple_data_type = assert_cast<const DataTypeTuple &>(*data_type);
                     size_t size_of_tuple = tuple_data_type.getElements().size();
 
-                    if (tuple_data_type.haveExplicitNames() && field_descriptor.message_type())
+                    if (const auto * message_type = field_descriptor.message_type())
                     {
+                        bool have_explicit_names = tuple_data_type.haveExplicitNames();
+                        Names element_names;
+                        if (have_explicit_names)
+                        {
+                            element_names = tuple_data_type.getElementNames();
+                        }
+                        else
+                        {
+                            /// Match unnamed Tuple elements and Message fields by position.
+                            size_t field_count = message_type->field_count();
+                            if (field_count != size_of_tuple)
+                                throw Exception(
+                                    ErrorCodes::NO_COLUMNS_SERIALIZED_TO_PROTOBUF_FIELDS,
+                                    "The number of fields in Protobuf message ({}) is not equal to the number of elements in unnamed Tuple ({})",
+                                    field_count,
+                                    size_of_tuple);
+                            for (size_t i = 0; i != field_count; ++i)
+                                element_names.push_back(message_type->field(static_cast<int>(i))->name());
+                        }
+
                         /// Try to serialize as a nested message.
                         std::vector<size_t> used_column_indices;
                         auto message_serializer = buildMessageSerializerImpl(
                             size_of_tuple,
-                            tuple_data_type.getElementNames().data(),
+                            element_names.data(),
                             tuple_data_type.getElements().data(),
-                            *field_descriptor.message_type(),
+                            *message_type,
                             /* with_length_delimiter = */ false,
                             google_wrappers_special_treatment,
                             &field_descriptor,

tests/queries/0_stateless/02707_protobuf_unnamed_tuple_as_nested_message.reference

@@ -0,0 +1 @@
+(42,'Hello',[1,2,3])

tests/queries/0_stateless/02707_protobuf_unnamed_tuple_as_nested_message.sh

@@ -0,0 +1,10 @@
+#!/usr/bin/env bash
+# Tags: no-fasttest
+
+CURDIR=$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)
+# shellcheck source=../shell_config.sh
+. "$CURDIR"/../shell_config.sh
+SCHEMADIR=$CURDIR/format_schemas
+
+$CLICKHOUSE_LOCAL -q "select tuple(42, 'Hello', [1,2,3]) as x format Protobuf settings format_schema='$SCHEMADIR/02707_schema:Message'" | $CLICKHOUSE_LOCAL --input-format Protobuf --structure='x Tuple(UInt32, String, Array(UInt32))' -q "select * from table" --format_schema="$SCHEMADIR/02707_schema:Message"
+

tests/queries/0_stateless/format_schemas/02707_schema.proto

@@ -0,0 +1,11 @@
+syntax = "proto3";
+
+message Nested {
+    int32 a = 1;
+    string b = 2;
+    repeated int32 c = 3;
+};
+
+message Message {
+    Nested x = 1;
+};