Improve support of Npgsql 4

- Integer types (Int32Type, Int64Type, etc) now convert argument to an expected type
before setting the parameter value.
- Since Npgsql 3.2.5, system transactions support has regressed. Disable some
of the tests that started failing with.

Author: hazzik

src/NHibernate.Test/NHibernate.Test.csproj

@@ -56,7 +56,7 @@
     <PackageReference Include="NUnit3TestAdapter" Version="3.10.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.5.0" />
     <PackageReference Include="FirebirdSql.Data.FirebirdClient" Version="6.3.0" />
-    <PackageReference Include="Npgsql" Version="3.2.4.1" />
+    <PackageReference Include="Npgsql" Version="4.0.3" />
   </ItemGroup>
   <ItemGroup Condition="'$(TargetFramework)'=='net461'">
     <Reference Include="System.Configuration" />

src/NHibernate.Test/TestDialects/PostgreSQL83TestDialect.cs

@@ -2,19 +2,19 @@
 {
 	public class PostgreSQL83TestDialect : TestDialect
 	{
-        public PostgreSQL83TestDialect(Dialect.Dialect dialect)
-            : base(dialect)
-        {
-        }
+		public PostgreSQL83TestDialect(Dialect.Dialect dialect)
+			: base(dialect)
+		{
+		}
 
-        public override bool SupportsSelectForUpdateOnOuterJoin
-        {
-            get { return false; }
-        }
+		public override bool SupportsSelectForUpdateOnOuterJoin => false;
 
-        public override bool SupportsNullCharactersInUtfStrings
-        {
-            get { return false; }
-        }
+		public override bool SupportsNullCharactersInUtfStrings => false;
+
+		/// <summary>
+		/// Npgsql since its 3.2.5 version fails some tests requiring this feature. The trouble was not occuring with
+		/// Npgsql 3.2.4.1.
+		/// </summary>
+		public override bool SupportsUsingConnectionOnSystemTransactionPrepare => false;
 	}
 }

src/NHibernate/Dialect/PostgreSQLDialect.cs

@@ -329,6 +329,16 @@ public override string CurrentTimestampSelectString
 
 		public override string QuerySequencesString => "SELECT c.relname FROM pg_class c WHERE c.relkind = 'S'";
 
+		/// <summary>
+		/// Does this dialect supports distributed transaction? <c>false</c>.
+		/// </summary>
+		/// <remarks>
+		/// Npgsql since its version 3.2.5 version has race conditions: it fails handling the threading involved with
+		/// distributed transactions. This causes a bunch of distributed tests to be flaky with Npgsql. Individually,
+		/// they usually succeed, but run together, some of them fail. The trouble was not occuring with Npgsql 3.2.4.1.
+		/// </remarks>
+		public override bool SupportsDistributedTransactions => false;
+
 		#endregion
 
 		[Serializable]

src/NHibernate/Type/DecimalType.cs

@@ -39,7 +39,7 @@ public override System.Type ReturnedClass
 
 		public override void Set(DbCommand st, object value, int index, ISessionImplementor session)
 		{
-			st.Parameters[index].Value = value;
+			st.Parameters[index].Value = Convert.ToDecimal(value);
 		}
 
 		public override string Name

src/NHibernate/Type/DoubleType.cs

@@ -38,7 +38,7 @@ public override System.Type ReturnedClass
 
 		public override void Set(DbCommand st, object value, int index, ISessionImplementor session)
 		{
-			st.Parameters[index].Value = value;
+			st.Parameters[index].Value = Convert.ToDouble(value);
 		}
 
 		/// <summary></summary>

src/NHibernate/Type/Int16Type.cs

@@ -58,7 +58,7 @@ public override System.Type ReturnedClass
 
 		public override void Set(DbCommand rs, object value, int index, ISessionImplementor session)
 		{
-			rs.Parameters[index].Value = value;
+			rs.Parameters[index].Value = Convert.ToInt16(value);
 		}
 
 		// 6.0 TODO: rename "xml" parameter as "value": it is not a xml string. The fact it generally comes from a xml

src/NHibernate/Type/Int32Type.cs

@@ -58,7 +58,7 @@ public override System.Type ReturnedClass
 
 		public override void Set(DbCommand rs, object value, int index, ISessionImplementor session)
 		{
-			rs.Parameters[index].Value = value;
+			rs.Parameters[index].Value = Convert.ToInt32(value);
 		}
 
 		// 6.0 TODO: rename "xml" parameter as "value": it is not a xml string. The fact it generally comes from a xml

src/NHibernate/Type/Int64Type.cs

@@ -58,7 +58,7 @@ public override System.Type ReturnedClass
 
 		public override void Set(DbCommand rs, object value, int index, ISessionImplementor session)
 		{
-			rs.Parameters[index].Value = value;
+			rs.Parameters[index].Value = Convert.ToInt64(value);
 		}
 
 		// 6.0 TODO: rename "xml" parameter as "value": it is not a xml string. The fact it generally comes from a xml

src/NHibernate/Type/SByteType.cs

@@ -58,7 +58,7 @@ public override System.Type ReturnedClass
 
 		public override void Set(DbCommand rs, object value, int index, ISessionImplementor session)
 		{
-			rs.Parameters[index].Value = value;
+			rs.Parameters[index].Value = Convert.ToSByte(value);
 		}
 
 		// 6.0 TODO: rename "xml" parameter as "value": it is not a xml string. The fact it generally comes from a xml

src/NHibernate/Type/UInt16Type.cs

@@ -58,7 +58,7 @@ public override System.Type ReturnedClass
 
 		public override void Set(DbCommand rs, object value, int index, ISessionImplementor session)
 		{
-			rs.Parameters[index].Value = value;
+			rs.Parameters[index].Value = Convert.ToUInt16(value);
 		}
 
 		// 6.0 TODO: rename "xml" parameter as "value": it is not a xml string. The fact it generally comes from a xml