Add field output_columns to first Result sent in gRPC protocol.

src/Server/GRPCServer.cpp

@@ -644,6 +644,7 @@ namespace
 
         void addQueryDetailsToResult();
         void addOutputFormatToResult();
+        void addOutputColumnsNamesAndTypesToResult(const Block & headers);
         void addProgressToResult();
         void addTotalsToResult(const Block & totals);
         void addExtremesToResult(const Block & extremes);
@@ -669,6 +670,7 @@ namespace
         CompressionMethod input_compression_method = CompressionMethod::None;
         PODArray<char> output;
         String output_format;
+        bool send_output_columns_names_and_types = false;
         CompressionMethod output_compression_method = CompressionMethod::None;
         int output_compression_level = 0;
 
@@ -890,6 +892,8 @@ namespace
         if (output_format.empty())
             output_format = query_context->getDefaultFormat();
 
+        send_output_columns_names_and_types = query_info.send_output_columns();
+
         /// Choose compression.
         String input_compression_method_str = query_info.input_compression_type();
         if (input_compression_method_str.empty())
@@ -1195,6 +1199,7 @@ namespace
             };
 
             addOutputFormatToResult();
+            addOutputColumnsNamesAndTypesToResult(header);
 
             Block block;
             while (check_for_cancel())
@@ -1457,6 +1462,18 @@ namespace
         *result.mutable_output_format() = output_format;
     }
 
+    void Call::addOutputColumnsNamesAndTypesToResult(const Block & header)
+    {
+        if (!send_output_columns_names_and_types)
+            return;
+        for (const auto & column : header)
+        {
+            auto & name_and_type = *result.add_output_columns();
+            *name_and_type.mutable_name() = column.name;
+            *name_and_type.mutable_type() = column.type->getName();
+        }
+    }
+
     void Call::addProgressToResult()
     {
         auto values = progress.fetchAndResetPiecewiseAtomically();

src/Server/grpc_protos/clickhouse_grpc.proto

@@ -82,6 +82,9 @@ message QueryInfo {
    // Default output format. If not specified, 'TabSeparated' is used.
    string output_format = 7;
 
+   // Set it if you want the names and the types of output columns to be sent to the client.
+   bool send_output_columns = 24;
+
    repeated ExternalTable external_tables = 8;
 
    string user_name = 9;
@@ -194,6 +197,9 @@ message Result {
    // It's either the same as `output_format` specified in `QueryInfo` or the format specified in the query itself.
    string output_format = 11;
 
+   // The names and types of columns of the result written in `output`.
+   repeated NameAndType output_columns = 12;
+
    // Output of the query, represented in the `output_format`.
    bytes output = 1;
    bytes totals = 2;

tests/integration/test_grpc_protocol/test.py

@@ -45,8 +45,8 @@ def create_channel():
         main_channel = channel
     return channel
 
-def query_common(query_text, settings={}, input_data=[], input_data_delimiter='', output_format='TabSeparated', external_tables=[],
-                 user_name='', password='', query_id='123', session_id='', stream_output=False, channel=None):
+def query_common(query_text, settings={}, input_data=[], input_data_delimiter='', output_format='TabSeparated', send_output_columns=False,
+                 external_tables=[], user_name='', password='', query_id='123', session_id='', stream_output=False, channel=None):
     if type(input_data) is not list:
         input_data = [input_data]
     if type(input_data_delimiter) is str:
@@ -60,7 +60,8 @@ def query_common(query_text, settings={}, input_data=[], input_data_delimiter=''
             input_data_part = input_data_part.encode(DEFAULT_ENCODING)
         return clickhouse_grpc_pb2.QueryInfo(query=query_text, settings=settings, input_data=input_data_part,
                                              input_data_delimiter=input_data_delimiter, output_format=output_format,
-                                             external_tables=external_tables, user_name=user_name, password=password, query_id=query_id,
+                                             send_output_columns=send_output_columns, external_tables=external_tables,
+                                             user_name=user_name, password=password, query_id=query_id,
                                              session_id=session_id, next_query_info=bool(input_data))
     def send_query_info():
         yield query_info()
@@ -211,18 +212,21 @@ def test_get_query_details():
     assert result.query_id == '123'
     pytz.timezone(result.time_zone)
     assert result.output_format == ''
+    assert len(result.output_columns) == 0
     assert result.output == b''
     #
     result = list(query_no_errors("SELECT 'a', 1", query_id = '', output_format = 'TabSeparated'))[0]
     uuid.UUID(result.query_id)
     pytz.timezone(result.time_zone)
     assert result.output_format == 'TabSeparated'
+    assert len(result.output_columns) == 0
     assert result.output == b'a\t1\n'
     #
-    result = list(query_no_errors("SELECT 'a' AS x, 1 FORMAT JSONEachRow", query_id = ''))[0]
+    result = list(query_no_errors("SELECT 'a' AS x, 1 FORMAT JSONEachRow", query_id = '', send_output_columns=True))[0]
     uuid.UUID(result.query_id)
     pytz.timezone(result.time_zone)
     assert result.output_format == 'JSONEachRow'
+    assert ([(col.name, col.type) for col in result.output_columns]) == [('x', 'String'), ('1', 'UInt8')]
     assert result.output == b'{"x":"a","1":1}\n'
 
 def test_errors_handling():