Proper query plan caching for DML LINQ queries (#2299)

Author: bahusoid

src/NHibernate.Test/Async/Linq/ConstantTest.cs

@@ -252,9 +252,10 @@ public async Task DmlPlansAreCachedAsync()
 			{
 				await (db.Customers.Where(c => c.CustomerId == "UNKNOWN").UpdateAsync(x => new Customer {CompanyName = "Constant1"}));
 				await (db.Customers.Where(c => c.CustomerId == "ALFKI").UpdateAsync(x => new Customer {CompanyName = x.CompanyName}));
+				await (db.Customers.Where(c => c.CustomerId == "UNKNOWN").UpdateAsync(x => new Customer {ContactName = "Constant1"}));
 				Assert.That(
 					cache,
-					Has.Count.EqualTo(2),
+					Has.Count.EqualTo(3),
 					"Query plans should be cached.");
 
 				using (var spy = new LogSpy(queryPlanCacheType))
@@ -264,6 +265,7 @@ public async Task DmlPlansAreCachedAsync()
 					{
 						await (db.Customers.Where(c => c.CustomerId == "ANATR").UpdateAsync(x => new Customer {CompanyName = x.CompanyName}));
 						await (db.Customers.Where(c => c.CustomerId == "UNKNOWN").UpdateAsync(x => new Customer {CompanyName = "Constant2"}));
+						await (db.Customers.Where(c => c.CustomerId == "UNKNOWN").UpdateAsync(x => new Customer {ContactName = "Constant2"}));
 
 						var sqlEvents = sqlSpy.Appender.GetEvents();
 						Assert.That(
@@ -272,19 +274,25 @@ public async Task DmlPlansAreCachedAsync()
 							"Unexpected constant parameter value");
 						Assert.That(
 							sqlEvents[1].RenderedMessage,
-							Does.Contain("UNKNOWN").And.Contain("Constant2").And.Not.Contain("Constant1"),
+							Does.Contain("UNKNOWN").And.Contain("Constant2").And.Contain("CompanyName").IgnoreCase
+								.And.Not.Contain("Constant1"),
+							"Unexpected constant parameter value");
+						Assert.That(
+							sqlEvents[2].RenderedMessage,
+							Does.Contain("UNKNOWN").And.Contain("Constant2").And.Contain("ContactName").IgnoreCase
+								.And.Not.Contain("Constant1"),
 							"Unexpected constant parameter value");
 					}
 
-					Assert.That(cache, Has.Count.EqualTo(2), "Additional queries should not cause a plan to be cached.");
+					Assert.That(cache, Has.Count.EqualTo(3), "Additional queries should not cause a plan to be cached.");
 					Assert.That(
 						spy.GetWholeLog(),
 						Does
 							.Contain("located HQL query plan in cache")
 							.And.Not.Contain("unable to locate HQL query plan in cache"));
 
 					await (db.Customers.Where(c => c.CustomerId == "ANATR").UpdateAsync(x => new Customer {ContactName = x.ContactName}));
-					Assert.That(cache, Has.Count.EqualTo(3), "Query should be cached");
+					Assert.That(cache, Has.Count.EqualTo(4), "Query should be cached");
 				}
 			}
 		}

src/NHibernate.Test/Linq/ConstantTest.cs

@@ -273,9 +273,10 @@ public void DmlPlansAreCached()
 			{
 				db.Customers.Where(c => c.CustomerId == "UNKNOWN").Update(x => new Customer {CompanyName = "Constant1"});
 				db.Customers.Where(c => c.CustomerId == "ALFKI").Update(x => new Customer {CompanyName = x.CompanyName});
+				db.Customers.Where(c => c.CustomerId == "UNKNOWN").Update(x => new Customer {ContactName = "Constant1"});
 				Assert.That(
 					cache,
-					Has.Count.EqualTo(2),
+					Has.Count.EqualTo(3),
 					"Query plans should be cached.");
 
 				using (var spy = new LogSpy(queryPlanCacheType))
@@ -285,6 +286,7 @@ public void DmlPlansAreCached()
 					{
 						db.Customers.Where(c => c.CustomerId == "ANATR").Update(x => new Customer {CompanyName = x.CompanyName});
 						db.Customers.Where(c => c.CustomerId == "UNKNOWN").Update(x => new Customer {CompanyName = "Constant2"});
+						db.Customers.Where(c => c.CustomerId == "UNKNOWN").Update(x => new Customer {ContactName = "Constant2"});
 
 						var sqlEvents = sqlSpy.Appender.GetEvents();
 						Assert.That(
@@ -293,19 +295,25 @@ public void DmlPlansAreCached()
 							"Unexpected constant parameter value");
 						Assert.That(
 							sqlEvents[1].RenderedMessage,
-							Does.Contain("UNKNOWN").And.Contain("Constant2").And.Not.Contain("Constant1"),
+							Does.Contain("UNKNOWN").And.Contain("Constant2").And.Contain("CompanyName").IgnoreCase
+								.And.Not.Contain("Constant1"),
+							"Unexpected constant parameter value");
+						Assert.That(
+							sqlEvents[2].RenderedMessage,
+							Does.Contain("UNKNOWN").And.Contain("Constant2").And.Contain("ContactName").IgnoreCase
+								.And.Not.Contain("Constant1"),
 							"Unexpected constant parameter value");
 					}
 
-					Assert.That(cache, Has.Count.EqualTo(2), "Additional queries should not cause a plan to be cached.");
+					Assert.That(cache, Has.Count.EqualTo(3), "Additional queries should not cause a plan to be cached.");
 					Assert.That(
 						spy.GetWholeLog(),
 						Does
 							.Contain("located HQL query plan in cache")
 							.And.Not.Contain("unable to locate HQL query plan in cache"));
 
 					db.Customers.Where(c => c.CustomerId == "ANATR").Update(x => new Customer {ContactName = x.ContactName});
-					Assert.That(cache, Has.Count.EqualTo(3), "Query should be cached");
+					Assert.That(cache, Has.Count.EqualTo(4), "Query should be cached");
 				}
 			}
 		}

src/NHibernate/Linq/DmlExpressionRewriter.cs

@@ -2,18 +2,13 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Linq.Expressions;
-using System.Reflection;
 using NHibernate.Linq.Visitors;
 using NHibernate.Util;
 
 namespace NHibernate.Linq
 {
 	public class DmlExpressionRewriter
 	{
-		static readonly ConstructorInfo DictionaryConstructorInfo = typeof(Dictionary<string, object>).GetConstructor(new[] {typeof(int)});
-
-		static readonly MethodInfo DictionaryAddMethodInfo = ReflectHelper.GetMethod<Dictionary<string, object>>(d => d.Add(null, null));
-
 		readonly IReadOnlyCollection<ParameterExpression> _parameters;
 		readonly Dictionary<string, Expression> _assignments = new Dictionary<string, Expression>();
 
@@ -80,39 +75,25 @@ void AddSettersFromAssignment(MemberAssignment assignment, string path)
 		}
 
 		/// <summary>
-		///     Converts the assignments into a lambda expression, which creates a Dictionary&lt;string,object%gt;.
+		///     Converts the assignments into block of assignments
 		/// </summary>
 		/// <param name="assignments"></param>
 		/// <returns>A lambda expression representing the assignments.</returns>
-		static LambdaExpression ConvertAssignmentsToDictionaryExpression<TSource>(IReadOnlyDictionary<string, Expression> assignments)
+		static LambdaExpression ConvertAssignmentsToBlockExpression<TSource>(IReadOnlyDictionary<string, Expression> assignments)
 		{
 			var param = Expression.Parameter(typeof(TSource));
-			var inits = new List<ElementInit>();
+			var variableAndAssignmentDic = new Dictionary<ParameterExpression, Expression>(assignments.Count);
 			foreach (var set in assignments)
 			{
 				var setter = set.Value;
 				if (setter is LambdaExpression setterLambda)
 					setter = setterLambda.Body.Replace(setterLambda.Parameters.First(), param);
-				inits.Add(
-					Expression.ElementInit(
-						DictionaryAddMethodInfo,
-						Expression.Constant(set.Key),
-						Expression.Convert(setter, typeof(object))));
+
+				var var = Expression.Variable(typeof(object), set.Key);
+				variableAndAssignmentDic[var] = Expression.Assign(var, Expression.Convert(setter, typeof(object)));
 			}
 
-			//The ListInit is intentionally "infected" with the lambda parameter (param), in the form of an IIF. 
-			//The only relevance is to make sure that the ListInit is not evaluated by the PartialEvaluatingExpressionTreeVisitor,
-			//which could turn it into a Constant
-			var listInit = Expression.ListInit(
-				Expression.New(
-					DictionaryConstructorInfo,
-					Expression.Condition(
-						Expression.Equal(param, Expression.Constant(null, typeof(TSource))),
-						Expression.Constant(assignments.Count),
-						Expression.Constant(assignments.Count))),
-				inits);
-
-			return Expression.Lambda(listInit, param);
+			return Expression.Lambda(Expression.Block(variableAndAssignmentDic.Keys, variableAndAssignmentDic.Values), param);
 		}
 
 		public static Expression PrepareExpression<TSource, TTarget>(Expression sourceExpression, Expression<Func<TSource, TTarget>> expression)
@@ -151,7 +132,7 @@ public static Expression PrepareExpressionFromAnonymous<TSource>(Expression sour
 
 		public static Expression PrepareExpression<TSource>(Expression sourceExpression, IReadOnlyDictionary<string, Expression> assignments)
 		{
-			var lambda = ConvertAssignmentsToDictionaryExpression<TSource>(assignments);
+			var lambda = ConvertAssignmentsToBlockExpression<TSource>(assignments);
 
 			return Expression.Call(
 				ReflectionCache.QueryableMethods.SelectDefinition.MakeGenericMethod(typeof(TSource), lambda.Body.Type),

src/NHibernate/Linq/NhLinqExpression.cs

@@ -88,16 +88,13 @@ public IASTNode Translate(ISessionFactoryImplementor sessionFactory, bool filter
 
 			ParameterDescriptors = requiredHqlParameters.AsReadOnly();
 
-			if (QueryMode == QueryMode.Select && CanCachePlan)
-			{
-				CanCachePlan =
-					// If some constants do not have matching HQL parameters, their values from first query will
-					// be embedded in the plan and reused for subsequent queries: do not cache the plan.
-					!ParameterValuesByName
+			CanCachePlan = CanCachePlan &&
+				// If some constants do not have matching HQL parameters, their values from first query will
+				// be embedded in the plan and reused for subsequent queries: do not cache the plan.
+				!ParameterValuesByName
 					.Keys
 					.Except(requiredHqlParameters.Select(p => p.Name))
 					.Any();
-			}
 
 			// The ast node may be altered by caller, duplicate it for preserving the original one.
 			return DuplicateTree(ExpressionToHqlTranslationResults.Statement.AstNode);

src/NHibernate/Linq/Visitors/QueryModelVisitor.cs

@@ -438,20 +438,20 @@ public override void VisitSelectClause(SelectClause selectClause, QueryModel que
 
 		private void VisitInsertClause(Expression expression)
 		{
-			var listInit = expression as ListInitExpression
+			var assignments = expression as BlockExpression
 				?? throw new QueryException("Malformed insert expression");
 			var insertedType = VisitorParameters.TargetEntityType;
 			var idents = new List<HqlIdent>();
 			var selectColumns = new List<HqlExpression>();
 
 			//Extract the insert clause from the projected ListInit
-			foreach (var assignment in listInit.Initializers)
+			foreach (BinaryExpression assignment in assignments.Expressions)
 			{
-				var member = (ConstantExpression)assignment.Arguments[0];
-				var value = assignment.Arguments[1];
+				var propName = ((ParameterExpression) assignment.Left).Name;
+				var value = assignment.Right;
 
 				//The target property
-				idents.Add(_hqlTree.TreeBuilder.Ident((string)member.Value));
+				idents.Add(_hqlTree.TreeBuilder.Ident(propName));
 
 				var valueHql = HqlGeneratorExpressionVisitor.Visit(value, VisitorParameters).AsExpression();
 				selectColumns.Add(valueHql);
@@ -467,16 +467,15 @@ private void VisitInsertClause(Expression expression)
 
 		private void VisitUpdateClause(Expression expression)
 		{
-			var listInit = expression as ListInitExpression
+			var assignments = expression as BlockExpression
 				?? throw new QueryException("Malformed update expression");
-			foreach (var initializer in listInit.Initializers)
+			foreach (BinaryExpression assigment in assignments.Expressions)
 			{
-				var member = (ConstantExpression)initializer.Arguments[0];
-				var setter = initializer.Arguments[1];
+				var propName = ((ParameterExpression) assigment.Left).Name;
+				var setter = assigment.Right;
 				var setterHql = HqlGeneratorExpressionVisitor.Visit(setter, VisitorParameters).AsExpression();
 
-				_hqlTree.AddSet(_hqlTree.TreeBuilder.Equality(_hqlTree.TreeBuilder.Ident((string)member.Value),
-					setterHql));
+				_hqlTree.AddSet(_hqlTree.TreeBuilder.Equality(_hqlTree.TreeBuilder.Ident(propName), setterHql));
 			}
 		}