Remove unnecessary ID increment in SequenceHiLoGenerator (#478)

Fixes #843

Author: livioc

src/NHibernate.Test/Async/NHSpecificTest/NH3879/Fixture3879.cs

@@ -0,0 +1,64 @@
+//------------------------------------------------------------------------------
+// <auto-generated>
+//     This code was generated by AsyncGenerator.
+//
+//     Changes to this file may cause incorrect behavior and will be lost if
+//     the code is regenerated.
+// </auto-generated>
+//------------------------------------------------------------------------------
+
+
+using System;
+using NUnit.Framework;
+
+namespace NHibernate.Test.NHSpecificTest.NH3879
+{
+	using System.Threading.Tasks;
+	[TestFixture]
+	public class Fixture3879Async : BugTestCase
+	{
+		protected override bool AppliesTo(Dialect.Dialect dialect)
+		{
+			return dialect.SupportsSequences;
+		}
+
+		[Test]
+		public async Task SeqhiloUsesFirstValidIdAsync()
+		{
+			//the first value of a sequence changes between the different databases (it can be 0 or 1)
+			//but the bug associated to this test happens only when it is different from zero so 
+			//we explicitly increment the sequence to ensure it
+			long previousSequenceValue;
+			using (var session = OpenSession())
+			{
+				var getSequenceSql = Dialect.GetSequenceNextValString("seqhiloEntity_ids");
+				//some adonet providers return an int, others a long
+				var boxedPreviousSequenceValue = await (session.CreateSQLQuery(getSequenceSql).UniqueResultAsync());
+				previousSequenceValue = Convert.ToInt64(boxedPreviousSequenceValue);
+			}
+
+			long id;
+			using (var session = OpenSession())
+			using (var tx = session.BeginTransaction())
+			{
+				var entity = new SeqhiloEntity();
+				await (session.SaveAsync(entity));
+				await (tx.CommitAsync());
+				id = entity.Id;
+			}
+
+			var expectedId = (previousSequenceValue + 1) * 10; //max_lo (9) + 1
+			Assert.That(id, Is.EqualTo(expectedId));
+		}
+
+		protected override void OnTearDown()
+		{
+			using (var session = OpenSession())
+			using (var tx = session.BeginTransaction())
+			{
+				session.CreateQuery("delete from SeqhiloEntity").ExecuteUpdate();
+				tx.Commit();
+			}
+		}
+	}
+}

src/NHibernate.Test/NHSpecificTest/NH3879/Fixture3879.cs

@@ -0,0 +1,53 @@
+using System;
+using NUnit.Framework;
+
+namespace NHibernate.Test.NHSpecificTest.NH3879
+{
+	[TestFixture]
+	public class Fixture3879 : BugTestCase
+	{
+		protected override bool AppliesTo(Dialect.Dialect dialect)
+		{
+			return dialect.SupportsSequences;
+		}
+
+		[Test]
+		public void SeqhiloUsesFirstValidId()
+		{
+			//the first value of a sequence changes between the different databases (it can be 0 or 1)
+			//but the bug associated to this test happens only when it is different from zero so 
+			//we explicitly increment the sequence to ensure it
+			long previousSequenceValue;
+			using (var session = OpenSession())
+			{
+				var getSequenceSql = Dialect.GetSequenceNextValString("seqhiloEntity_ids");
+				//some adonet providers return an int, others a long
+				var boxedPreviousSequenceValue = session.CreateSQLQuery(getSequenceSql).UniqueResult();
+				previousSequenceValue = Convert.ToInt64(boxedPreviousSequenceValue);
+			}
+
+			long id;
+			using (var session = OpenSession())
+			using (var tx = session.BeginTransaction())
+			{
+				var entity = new SeqhiloEntity();
+				session.Save(entity);
+				tx.Commit();
+				id = entity.Id;
+			}
+
+			var expectedId = (previousSequenceValue + 1) * 10; //max_lo (9) + 1
+			Assert.That(id, Is.EqualTo(expectedId));
+		}
+
+		protected override void OnTearDown()
+		{
+			using (var session = OpenSession())
+			using (var tx = session.BeginTransaction())
+			{
+				session.CreateQuery("delete from SeqhiloEntity").ExecuteUpdate();
+				tx.Commit();
+			}
+		}
+	}
+}

src/NHibernate.Test/NHSpecificTest/NH3879/Mappings.hbm.xml

@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="utf-8" ?> 
+<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
+	assembly="NHibernate.Test"
+	namespace="NHibernate.Test.NHSpecificTest.NH3879"
+	default-lazy="false">
+
+  <class name="SeqhiloEntity" table="SeqhiloEntity">
+    <id name="Id" type="Int64">
+      <generator class="seqhilo" >
+        <param name="max_lo">9</param>
+        <param name="sequence">seqhiloEntity_ids</param>
+      </generator>
+    </id>
+  </class>
+
+</hibernate-mapping>

src/NHibernate.Test/NHSpecificTest/NH3879/SeqhiloEntity.cs

@@ -0,0 +1,7 @@
+namespace NHibernate.Test.NHSpecificTest.NH3879
+{
+	public class SeqhiloEntity
+	{
+		public long Id { get; set; }
+	}
+}

src/NHibernate/Async/Id/SequenceHiLoGenerator.cs

@@ -53,7 +53,7 @@ public override async Task<object> GenerateAsync(ISessionImplementor session, ob
 				if (lo > maxLo)
 				{
 					long hival = Convert.ToInt64(await (base.GenerateAsync(session, obj, cancellationToken)).ConfigureAwait(false));
-					lo = 1;
+					lo = (hival == 0) ? 1 : 0;
 					hi = hival * (maxLo + 1);
 					if (log.IsDebugEnabled)
 						log.Debug("new hi value: " + hival);

src/NHibernate/Id/SequenceHiLoGenerator.cs

@@ -90,7 +90,7 @@ public override object Generate(ISessionImplementor session, object obj)
 			if (lo > maxLo)
 			{
 				long hival = Convert.ToInt64(base.Generate(session, obj));
-				lo = 1;
+				lo = (hival == 0) ? 1 : 0;
 				hi = hival * (maxLo + 1);
 				if (log.IsDebugEnabled)
 					log.Debug("new hi value: " + hival);