feat: generate DECLARE AS (#183)

Author: KirillKurdyukov

src/Ydb.Sdk/src/Ado/YdbCommand.cs

@@ -1,5 +1,7 @@
 using System.Data;
 using System.Data.Common;
+using System.Text;
+using Ydb.Sdk.Ado.Internal;
 using Ydb.Sdk.Services.Query;
 
 namespace Ydb.Sdk.Ado;
@@ -171,12 +173,30 @@ protected override async Task<DbDataReader> ExecuteDbDataReaderAsync(CommandBeha
             throw new YdbOperationInProgressException(YdbConnection);
         }
 
+        var ydbParameters = DbParameterCollection.YdbParameters;
+        var (sql, paramNames) = SqlParser.Parse(CommandText);
+        var preparedSql = new StringBuilder();
+
+        foreach (var paramName in paramNames)
+        {
+            if (ydbParameters.TryGetValue(paramName, out var ydbValue))
+            {
+                preparedSql.Append($"DECLARE {paramName} AS {ydbValue.ToYql()};\n");
+            }
+            else
+            {
+                throw new YdbException($"Not found YDB parameter [name: {paramName}]");
+            }
+        }
+
+        preparedSql.Append(sql);
+
         var execSettings = CommandTimeout > 0
             ? new ExecuteQuerySettings { TransportTimeout = TimeSpan.FromSeconds(CommandTimeout) }
             : ExecuteQuerySettings.DefaultInstance;
 
         var ydbDataReader = await YdbDataReader.CreateYdbDataReader(YdbConnection.Session.ExecuteQuery(
-                _commandText, DbParameterCollection.YdbParameters, execSettings, Transaction?.TransactionControl),
+                preparedSql.ToString(), ydbParameters, execSettings, Transaction?.TransactionControl),
             YdbConnection.Session.OnStatus, Transaction);
 
         YdbConnection.LastReader = ydbDataReader;

src/Ydb.Sdk/src/Value/YdbValue.cs

@@ -56,11 +56,9 @@ internal YdbValue(Type type, Ydb.Value value)
     {
         _protoType = type;
         _protoValue = value;
-
-        TypeId = GetYdbTypeId(type);
     }
 
-    public YdbTypeId TypeId { get; }
+    public YdbTypeId TypeId => GetYdbTypeId(_protoType);
 
     public TypedValue GetProto()
     {
@@ -76,6 +74,24 @@ public override string ToString()
         return _protoValue.ToString() ?? "";
     }
 
+    internal string ToYql()
+    {
+        return ToYql(_protoType);
+    }
+
+    private static string ToYql(Type type)
+    {
+        return type.TypeCase switch
+        {
+            Type.TypeOneofCase.TypeId => type.TypeId.ToString(),
+            Type.TypeOneofCase.DecimalType => "Decimal(22, 9)",
+            Type.TypeOneofCase.OptionalType => $"{ToYql(type.OptionalType.Item)}?",
+            Type.TypeOneofCase.ListType => $"List<{ToYql(type.ListType.Item)}>",
+            Type.TypeOneofCase.VoidType => "Void",
+            _ => "Unknown"
+        };
+    }
+
     internal static YdbTypeId GetYdbTypeId(Type protoType)
     {
         return protoType.TypeCase switch

src/Ydb.Sdk/tests/Ado/YdbCommandTests.cs

@@ -43,6 +43,30 @@ public async Task ExecuteScalarAsync_WhenSetYdbParameter_ReturnThisValue<T>(YdbP
         }
     }
 
+    [Theory]
+    [ClassData(typeof(YdbParameterTests.TestDataGenerator))]
+    public async Task ExecuteScalarAsync_WhenSetYdbParameterThenPrepare_ReturnThisValue<T>(
+        YdbParameterTests.Data<T> data)
+    {
+        await using var connection = new YdbConnection();
+        await connection.OpenAsync();
+
+        var dbCommand = connection.CreateCommand();
+
+        dbCommand.CommandText = "SELECT @var;";
+
+        var dbParameter = new YdbParameter
+        {
+            ParameterName = "@var",
+            DbType = data.DbType,
+            Value = data.Expected,
+            IsNullable = data.IsNullable
+        };
+        dbCommand.Parameters.Add(dbParameter);
+
+        Assert.Equal(data.Expected, await dbCommand.ExecuteScalarAsync());
+    }
+
     [Fact]
     public async Task ExecuteNonQueryAsync_WhenCreateUser_ReturnEmptyResultSet()
     {