Fix for NH-3436

Author: hazzik

src/NHibernate/Engine/Query/HQLExpressionQueryPlan.cs

@@ -14,6 +14,17 @@ public IQueryExpression QueryExpression
             protected set;
         }
 
+		private HQLExpressionQueryPlan(HQLQueryPlan source, IQueryExpression newQueryExpression)
+			: base(source)
+		{
+			QueryExpression = newQueryExpression;
+		}
+
+		internal HQLExpressionQueryPlan Copy(IQueryExpression newExpression)
+		{
+			return new HQLExpressionQueryPlan(this, newExpression);
+		}
+
         public HQLExpressionQueryPlan(string expressionStr, IQueryExpression queryExpression, bool shallow,
                                       IDictionary<string, IFilter> enabledFilters, ISessionFactoryImplementor factory)
             : this(expressionStr, queryExpression, null, shallow, enabledFilters, factory)

src/NHibernate/Engine/Query/HQLQueryPlan.cs

@@ -5,6 +5,7 @@
 
 using NHibernate.Event;
 using NHibernate.Hql;
+using NHibernate.Linq;
 using NHibernate.Type;
 using NHibernate.Util;
 
@@ -43,6 +44,16 @@ protected HQLQueryPlan(string sourceQuery, IQueryTranslator[] translators)
             FinaliseQueryPlan();
         }
 
+		internal HQLQueryPlan(HQLQueryPlan source)
+		{
+			Translators = source.Translators;
+			_sourceQuery = source._sourceQuery;
+			QuerySpaces = source.QuerySpaces;
+			ParameterMetadata = source.ParameterMetadata;
+			ReturnMetadata = source.ReturnMetadata;
+			SqlStrings = source.SqlStrings;
+		}
+
 	    public ISet<string> QuerySpaces
 		{
 		    get;

src/NHibernate/Engine/Query/QueryPlanCache.cs

@@ -78,7 +78,7 @@ public IQueryExpressionPlan GetHQLQueryPlan(IQueryExpression queryExpression, bo
 			string expressionStr = queryExpression.Key;
 
 			var key = new HQLQueryPlanKey(queryExpression, shallow, enabledFilters);
-			var plan = (IQueryExpressionPlan)planCache[key];
+			var plan = (HQLExpressionQueryPlan) planCache[key];
 
 			if (plan == null)
 			{
@@ -105,8 +105,12 @@ public IQueryExpressionPlan GetHQLQueryPlan(IQueryExpression queryExpression, bo
 					// for cases when we have list parameters in query, like @p1.Contains(...),
 					// it does, and then it uses parameters from first try. 
 					//TODO: cache only required parts of QueryExpression
-					planExpression._expression = expression._expression;
-					planExpression._constantToParameterMap = expression._constantToParameterMap;
+
+					//NH-3436
+					// We have to return new instance plan with it's own query expression
+					// because other treads can override queryexpression of current plan during execution of query if we will use cached instance of plan 
+					expression.CopyExpressionTranslation(planExpression);
+					plan = plan.Copy(expression);
 				}
 			}
 

src/NHibernate/Linq/NhLinqExpression.cs

@@ -1,4 +1,5 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
 using System.Linq;
 using System.Linq.Expressions;
 using NHibernate.Engine;
@@ -70,5 +71,11 @@ public IASTNode Translate(ISessionFactoryImplementor sessionFactory)
 
 			return ExpressionToHqlTranslationResults.Statement.AstNode;
 		}
+
+		internal void CopyExpressionTranslation(NhLinqExpression other)
+		{
+			ExpressionToHqlTranslationResults = other.ExpressionToHqlTranslationResults;
+			ParameterDescriptors = other.ParameterDescriptors;
+		}
 	}
 }