resolve some conversations

Author: XmasApple

examples/src/QueryExample/QueryExample.cs

@@ -207,7 +207,8 @@ private async Task InteractiveTx()
                     PRAGMA TablePathPrefix('{BasePath}');
 
                     SELECT first_aired FROM seasons
-                    WHERE series_id = $series_id AND season_id = $season_id;
+                    WHERE series_id = $series_id AND season_id = $season_id
+                    LIMIT 1;
                 ";
                 var parameters1 = new Dictionary<string, YdbValue>
                 {
@@ -254,22 +255,31 @@ private async Task StreamSelect()
                 ";
 
 
-        await Client.Query(
+        var response = await Client.Query(
             query,
             func: async stream =>
             {
+                var result = new List<Series>();
                 await foreach (var part in stream)
                 {
                     if (part.ResultSet == null) continue;
                     foreach (var row in part.ResultSet.Rows)
                     {
-                        Console.WriteLine(Series.FromRow(row));
+                        result.Add(Series.FromRow(row));
                     }
                 }
 
-                return stream.Next();
+                return result;
             }
         ).ConfigureAwait(false);
+        response.EnsureSuccess();
+        if (response.Result != null)
+        {
+            foreach (var series in response.Result)
+            {
+                Console.WriteLine(series);
+            }
+        }
     }
 
     private async Task ReadScalar()
@@ -362,6 +372,7 @@ private async Task ReadAllResultSets()
         {
             Console.WriteLine($"\t\t{Series.FromRow(row)}");
         }
+
         Console.WriteLine("\t'episodes' contains:");
         foreach (var row in episodesSet)
         {

src/Ydb.Sdk/src/Services/Query/QueryClient.cs

@@ -180,6 +180,10 @@ public async Task<QueryResponse> Exec(string queryString,
     internal static async Task<YdbValue> ReadScalarHelper(ExecuteQueryStream stream)
     {
         var row = await ReadSingleRowHelper(stream);
+        if (row.ColumnCount != 1)
+        {
+            throw new QueryWrongResultFormatException("Row should contain exactly one field");
+        }
         return row[0];
     }
 

src/Ydb.Sdk/src/Value/ResultSet.cs

@@ -129,5 +129,7 @@ internal Row(Ydb.Value row, IReadOnlyList<Column> columns, IReadOnlyDictionary<s
         public YdbValue this[int columnIndex] => new(_columns[columnIndex].Type, _row.Items[columnIndex]);
 
         public YdbValue this[string columnName] => this[_columnsMap[columnName]];
+
+        internal int ColumnCount => _columns.Count;
     }
 }

src/Ydb.Sdk/tests/Query/TestQueryIntegration.cs

@@ -62,23 +62,23 @@ public async Task TestSimpleSelect()
         });
 
         var responseAllRows = await client.ReadAllRows(queryString);
-        var responseFirstRow = await client.ReadSingleRow(queryString); // ReadOneRow
+        var responseSingleRow = await client.ReadSingleRow(queryString); // ReadOneRow
 
         Assert.Equal(StatusCode.Success, responseQuery.Status.StatusCode);
         Assert.Equal(StatusCode.Success, responseAllRows.Status.StatusCode);
-        Assert.Equal(StatusCode.Success, responseFirstRow.Status.StatusCode);
+        Assert.Equal(StatusCode.Success, responseSingleRow.Status.StatusCode);
         Assert.NotNull(responseQuery.Result);
-        Assert.NotNull(responseFirstRow.Result);
+        Assert.NotNull(responseSingleRow.Result);
         Assert.NotNull(responseAllRows.Result);
         Assert.Single(responseQuery.Result!);
         Assert.Single(responseAllRows.Result!);
 
         var valueQuery = (int)responseQuery.Result!.First()["sum"];
         var valueReadAll = (int)responseAllRows.Result!.First()["sum"];
-        var valueReadFirst = (int)responseFirstRow.Result!["sum"];
+        var valueReadSingle = (int)responseSingleRow.Result!["sum"];
 
         Assert.Equal(valueQuery, valueReadAll);
-        Assert.Equal(valueQuery, valueReadFirst);
+        Assert.Equal(valueQuery, valueReadSingle);
         Assert.Equal(5, valueQuery);
     }
 
@@ -326,6 +326,8 @@ await Assert.ThrowsAsync<QueryWrongResultFormatException>(() =>
                 client.ReadScalar(SelectMultipleResultSetsQuery));
             await Assert.ThrowsAsync<QueryWrongResultFormatException>(() =>
                 client.ReadScalar(SelectMultipleRowsQuery));
+            await Assert.ThrowsAsync<QueryWrongResultFormatException>(() =>
+                client.ReadScalar(SelectSingleRowQuery));
             var response = await client.ReadScalar(SelectScalarQuery);
             var resultSet = response.Result;
             Assert.NotNull(resultSet);