Fix NH-3142 by having the JoinWalker avoid reusing Parameter instance…

…s. Parameter instances are later assigned a value to their BackTrack property. If the same instance is used in multiple positions the BackTracks will be incorrect, since all occurrences will get the same BackTrack and therefore the same value. But in this situation, they really do represent separate values.

src/NHibernate/Loader/JoinWalker.cs

@@ -772,29 +772,29 @@ protected SqlStringBuilder WhereString(string alias, string[] columnNames, int b
 			}
 			else
 			{
-				Parameter[] columnParameters = Parameter.GenerateParameters(columnNames.Length);
-				ConditionalFragment byId = new ConditionalFragment()
-					.SetTableAlias(alias)
-					.SetCondition(columnNames, columnParameters);
+				var fragments = new ConditionalFragment[batchSize];
+				for (int i = 0; i < batchSize; i++)
+				{
+					fragments[i] = new ConditionalFragment()
+						.SetTableAlias(alias)
+						.SetCondition(columnNames, Parameter.GenerateParameters(columnNames.Length));
+				}
 
-				SqlStringBuilder whereString = new SqlStringBuilder();
+				var whereString = new SqlStringBuilder();
 
-				if (batchSize == 1)
+				if (fragments.Length == 1)
 				{
 					// if no batch, use "foo = ? and bar = ?"
-					whereString.Add(byId.ToSqlStringFragment());
+					whereString.Add(fragments[0].ToSqlStringFragment());
 				}
 				else
 				{
-					// if a composite key, use "( (foo = ? and bar = ?) or (foo = ? and bar = ?) )" for batching
-					whereString.Add(StringHelper.OpenParen); // TODO: unnecessary for databases with ANSI-style joins
-					DisjunctionFragment df = new DisjunctionFragment();
-					for (int i = 0; i < batchSize; i++)
-					{
-						df.AddCondition(byId);
-					}
+					// if batching, use "( (foo = ? and bar = ?) or (foo = ? and bar = ?) )"
+					var df = new DisjunctionFragment(fragments);
+
+					whereString.Add(StringHelper.OpenParen);
 					whereString.Add(df.ToFragmentString());
-					whereString.Add(StringHelper.ClosedParen); // TODO: unnecessary for databases with ANSI-style joins
+					whereString.Add(StringHelper.ClosedParen);
 				}
 
 				return whereString;

src/NHibernate/SqlCommand/DisjunctionFragment.cs

@@ -1,11 +1,24 @@
 using System;
+using System.Collections.Generic;
 
 namespace NHibernate.SqlCommand
 {
 	public class DisjunctionFragment
 	{
 		private SqlStringBuilder buffer = new SqlStringBuilder();
 
+		public DisjunctionFragment()
+		{
+		}
+
+
+		public DisjunctionFragment(IEnumerable<ConditionalFragment> fragments)
+		{
+			foreach (var conditionalFragment in fragments)
+				AddCondition(conditionalFragment);
+		}
+
+
 		public DisjunctionFragment AddCondition(ConditionalFragment fragment)
 		{
 			if (buffer.Count > 0)