Fix ColumnSize evaluation in .NET connector

Summary: 'ColumnSize' of the text type starting from version 7.8 is received in characters (previously in bytes) (see the diff, https://grizzly.internal.memcompute.com/D54237)

Test Plan: https://app.circleci.com/pipelines/github/memsql/SingleStoreNETConnector/217/workflows/9fb63d7c-cf09-49b1-9495-be75cb69493e

Reviewers: pmishchenko-ua

Reviewed By: pmishchenko-ua

Subscribers: engineering-list

JIRA Issues: PLAT-6219

Differential Revision: https://grizzly.internal.memcompute.com/D56875

src/SingleStoreConnector/SingleStoreDataReader.cs

@@ -345,7 +345,7 @@ public ReadOnlyCollection<DbColumn> GetColumnSchema()
 		var hasNoSchema = columnDefinitions is null || m_resultSet!.ContainsCommandParameters;
 		return hasNoSchema ? new List<DbColumn>().AsReadOnly() :
 			columnDefinitions!
-				.Select((c, n) => (DbColumn) new SingleStoreDbColumn(n, c, Connection!.AllowZeroDateTime, GetResultSet().ColumnTypes![n]))
+				.Select((c, n) => (DbColumn) new SingleStoreDbColumn(n, c, Connection!.AllowZeroDateTime, GetResultSet().ColumnTypes![n], Connection.Session.S2ServerVersion.Version))
 				.ToList().AsReadOnly();
 	}
 

src/SingleStoreConnector/SingleStoreDbColumn.cs

@@ -44,18 +44,30 @@ namespace SingleStoreConnector
 {
 	public sealed class SingleStoreDbColumn : System.Data.Common.DbColumn
 	{
-		internal SingleStoreDbColumn(int ordinal, ColumnDefinitionPayload column, bool allowZeroDateTime, SingleStoreDbType mySqlDbType)
+		internal SingleStoreDbColumn(int ordinal, ColumnDefinitionPayload column, bool allowZeroDateTime, SingleStoreDbType mySqlDbType, Version serverVersion)
 		{
 			var columnTypeMetadata = TypeMapper.Instance.GetColumnTypeMetadata(mySqlDbType);
 
 			var type = columnTypeMetadata.DbTypeMapping.ClrType;
 
-			if (mySqlDbType == SingleStoreDbType.JSON || mySqlDbType == SingleStoreDbType.LongBlob)
-				ColumnSize = int.MaxValue;
+			// starting from 7.8 SingleStore returns number of characters (not amount of bytes)
+			// for text types (e.g. Text, TinyText, MediumText, LongText)
+			// (see https://grizzly.internal.memcompute.com/D54237)
+			if (serverVersion >= new Version(7, 8, 0) &&
+			    mySqlDbType is SingleStoreDbType.LongText or SingleStoreDbType.MediumText or SingleStoreDbType.Text or SingleStoreDbType.TinyText)
+			{
+				// overflow may occur here for SingleStoreDbType.LongText
+				ColumnSize = (int)column.ColumnLength;
+			}
 			else
+			{
+				if (mySqlDbType == SingleStoreDbType.JSON || mySqlDbType == SingleStoreDbType.LongBlob)
+					ColumnSize = int.MaxValue;
+				else
 
-				// overflow may occur here
-				ColumnSize = (int) (column.ColumnLength / ProtocolUtility.GetBytesPerCharacter(column.CharacterSet));
+					// overflow may occur here
+					ColumnSize = (int) (column.ColumnLength / ProtocolUtility.GetBytesPerCharacter(column.CharacterSet));
+			}
 
 			// if overflow occured, i.e. when column.ColumnLength > int.MaxValue and char size was 1,
 			// we set ColumnSize to max
@@ -69,7 +81,6 @@ internal SingleStoreDbColumn(int ordinal, ColumnDefinitionPayload column, bool a
 			BaseTableName = column.PhysicalTable;
 			ColumnName = column.Name;
 			ColumnOrdinal = ordinal;
-
 			DataType = (allowZeroDateTime && type == typeof(DateTime)) ? typeof(SingleStoreDateTime) : type;
 			DataTypeName = columnTypeMetadata.SimpleDataTypeName;
 			if (mySqlDbType == SingleStoreDbType.String)

tests/SideBySide/BulkLoaderSync.cs

@@ -815,7 +815,7 @@ public void BulkCopyColumnMappings()
 		Assert.Equal(3, result.RowsInserted);
 		Assert.Empty(result.Warnings);
 
-		using var reader = connection.ExecuteReader(@"select * from bulk_copy_column_mapping;");
+		using var reader = connection.ExecuteReader(@"select * from bulk_copy_column_mapping order by intvalue;");
 		Assert.True(reader.Read());
 		Assert.Equal(101, reader.GetValue(0));
 		Assert.Equal("A", reader.GetValue(1));