private static TimeSpan RefreshUtcOffset(ISessionFactory sessionWrapper, ProviderTypeEnum providerType)
{
lock (DateOffsetMutex)
{
Func <object, DateTime> conversionFunc = a => (DateTime)a;
using (var session = sessionWrapper.OpenStatelessSession())
{
IQuery query = null;
switch (providerType == ProviderTypeEnum.None
? sessionWrapper.DeriveProviderType()
: providerType)
{
case ProviderTypeEnum.OracleClient10Managed:
case ProviderTypeEnum.OracleClient9Managed:
case ProviderTypeEnum.OracleClient10:
case ProviderTypeEnum.OracleClient9:
query = session.CreateSQLQuery("select systimestamp at time zone 'UTC' from dual");
break;
case ProviderTypeEnum.PostgreSQLStandard:
case ProviderTypeEnum.PostgreSQL81:
case ProviderTypeEnum.PostgreSQL82:
query = session.CreateSQLQuery("SELECT NOW() at time zone 'utc'");
break;
case ProviderTypeEnum.MySQL:
query = session.CreateSQLQuery("select utc_timestamp()");
break;
case ProviderTypeEnum.JetDriver:
case ProviderTypeEnum.SQLite:
query = null;
break;
case ProviderTypeEnum.DB2Informix1150:
query = session.CreateSQLQuery("select dbinfo('utc_current')");
conversionFunc = o =>
{
var seconds = Convert.ToInt32(o);
return(new DateTime(1970, 1, 1).AddSeconds(seconds));
};
break;
case ProviderTypeEnum.SQLAnywhere10:
case ProviderTypeEnum.SQLAnywhere9:
case ProviderTypeEnum.SQLAnywhere11:
case ProviderTypeEnum.SQLAnywhere12:
query = session.CreateSQLQuery("select CURRENT UTC TIMESTAMP");
break;
case ProviderTypeEnum.MsSql2000:
case ProviderTypeEnum.MsSql2005:
case ProviderTypeEnum.MsSql2008:
case ProviderTypeEnum.MsSql2012:
query = session.CreateSQLQuery("select getutcdate()");
break;
case ProviderTypeEnum.DB2Standard:
query = session.CreateSQLQuery("select CURRENT TIMESTAMP - CURRENT TIME ZONE");
break;
case ProviderTypeEnum.Firebird:
case ProviderTypeEnum.MsSqlCe40:
default:
throw new NotImplementedException(
string.Format("This feature is not supported for provider {0}",
providerType == ProviderTypeEnum.None
? sessionWrapper.DeriveProviderType()
: providerType));
}
if (query != null)
{
var stopwatch = new Stopwatch();
var current = DateTime.UtcNow;
stopwatch.Start();
var serverUtc = conversionFunc(query.UniqueResult());
stopwatch.Stop();
return(serverUtc.Subtract(current).Subtract(stopwatch.Elapsed));
}
return(TimeSpan.Zero);
}
}
}
