Respect CommandBehavior.SchemaOnly. Fixes #723

Author: bgrainger

src/MySqlConnector/Core/SingleCommandPayloadCreator.cs

@@ -173,7 +173,7 @@ private static bool WriteStoredProcedure(IMySqlCommand command, IDictionary<stri
 			if (returnParameter is null)
 			{
 				commandText = inOutSetParameters + "CALL " + commandText;
-				if (outParameters.Count > 0)
+				if (outParameters.Count > 0 && (command.CommandBehavior & CommandBehavior.SchemaOnly) == 0)
 				{
 					commandText += "SELECT '" + OutParameterSentinelColumnName + "' AS '" + OutParameterSentinelColumnName + "', " + string.Join(", ", outParameterNames);
 				}
@@ -191,17 +191,21 @@ private static bool WriteStoredProcedure(IMySqlCommand command, IDictionary<stri
 
 		private static bool WriteCommand(IMySqlCommand command, ByteBufferWriter writer)
 		{
+			var isSchemaOnly = (command.CommandBehavior & CommandBehavior.SchemaOnly) != 0;
 			var isSingleRow = (command.CommandBehavior & CommandBehavior.SingleRow) != 0;
-			if (isSingleRow)
-				writer.Write(SetSqlSelectLimit);
+			if (isSchemaOnly)
+				writer.Write(SetSqlSelectLimit0);
+			else if (isSingleRow)
+				writer.Write(SetSqlSelectLimit1);
 			var preparer = new StatementPreparer(command.CommandText!, command.RawParameters, command.CreateStatementPreparerOptions());
 			var isComplete = preparer.ParseAndBindParameters(writer);
-			if (isComplete && isSingleRow)
+			if (isComplete && (isSchemaOnly || isSingleRow))
 				writer.Write(ClearSqlSelectLimit);
 			return isComplete;
 		}
 
-		static ReadOnlySpan<byte> SetSqlSelectLimit => new byte[] { 83, 69, 84, 32, 115, 113, 108, 95, 115, 101, 108, 101, 99, 116, 95, 108, 105, 109, 105, 116, 61, 49, 59, 10 }; // SET sql_select_limit=1;\n
+		static ReadOnlySpan<byte> SetSqlSelectLimit0 => new byte[] { 83, 69, 84, 32, 115, 113, 108, 95, 115, 101, 108, 101, 99, 116, 95, 108, 105, 109, 105, 116, 61, 48, 59, 10 }; // SET sql_select_limit=0;\n
+		static ReadOnlySpan<byte> SetSqlSelectLimit1 => new byte[] { 83, 69, 84, 32, 115, 113, 108, 95, 115, 101, 108, 101, 99, 116, 95, 108, 105, 109, 105, 116, 61, 49, 59, 10 }; // SET sql_select_limit=1;\n
 		static ReadOnlySpan<byte> ClearSqlSelectLimit => new byte[] { 10, 83, 69, 84, 32, 115, 113, 108, 95, 115, 101, 108, 101, 99, 116, 95, 108, 105, 109, 105, 116, 61, 100, 101, 102, 97, 117, 108, 116, 59 }; // \nSET sql_select_limit=default;
 		static readonly IMySqlConnectorLogger Log = MySqlConnectorLogManager.CreateLogger(nameof(SingleCommandPayloadCreator));
 	}

tests/SideBySide/DataTypes.cs

@@ -1096,7 +1096,8 @@ private void DoGetSchemaTable(string column, string table, MySqlDbType mySqlDbTy
 			command.CommandText = $"select `{column}` from `{table}`;";
 			command.Prepare();
 
-			using var reader = command.ExecuteReader();
+			using var reader = command.ExecuteReader(CommandBehavior.SchemaOnly);
+			Assert.False(reader.Read());
 			var schemaTable = reader.GetSchemaTable();
 			Assert.Single(schemaTable.Rows);
 			var schema = schemaTable.Rows[0];