ExpressionProcessor prefers Case over Variant in most cases

Author: alex-kulakov

Orm/Xtensive.Orm/Orm/Providers/Expressions/ExpressionProcessor.cs

@@ -352,8 +352,10 @@ protected override SqlExpression VisitConditional(ConditionalExpression expressi
         ? booleanExpressionConverter.BooleanToInt(check)
         : check;
       var varCheck = boolCheck as SqlVariant;
-      if (!PreferCaseOverVariant && !varCheck.IsNullReference())
+
+      if (!PreferCaseOverVariant && !varCheck.IsNullReference()) {
         return SqlDml.Variant(varCheck.Id, ifFalse, ifTrue);
+      }
       var @case = SqlDml.Case();
       if (fixExpressions && IsBooleanExpression(expression)) {
         @case[check] = booleanExpressionConverter.BooleanToInt(ifTrue);
@@ -482,8 +484,11 @@ private SqlExpression TryUnwrapEnum(SqlContainer container)
 
     // Constructors
 
-    public ExpressionProcessor(
-      LambdaExpression lambda, HandlerAccessor handlers, SqlCompiler compiler, in bool preferCaseOverVariant, params IReadOnlyList<SqlExpression>[] sourceColumns)
+    public ExpressionProcessor(LambdaExpression lambda,
+      HandlerAccessor handlers,
+      SqlCompiler compiler,
+      in bool preferCaseOverVariant,
+      params IReadOnlyList<SqlExpression>[] sourceColumns)
     {
       ArgumentValidator.EnsureArgumentNotNull(lambda, "lambda");
       ArgumentValidator.EnsureArgumentNotNull(handlers, "handlers");

Orm/Xtensive.Orm/Orm/Providers/SqlCompiler.Helpers.cs

@@ -60,10 +60,10 @@ protected SqlProvider CreateProvider(SqlSelect statement, IEnumerable<QueryParam
 
     protected virtual string ProcessAliasedName(string name) => name;
 
-    protected Pair<SqlExpression, IEnumerable<QueryParameterBinding>> ProcessExpression(LambdaExpression le,
+    protected Pair<SqlExpression, IEnumerable<QueryParameterBinding>> ProcessExpression(LambdaExpression le, in bool preferCaseOverVariant,
       params IReadOnlyList<SqlExpression>[] sourceColumns)
     {
-      var processor = new ExpressionProcessor(le, Handlers, this, (Owner ?? RootProvider).Type == ProviderType.Sort, sourceColumns);
+      var processor = new ExpressionProcessor(le, Handlers, this, preferCaseOverVariant, sourceColumns);
       var result = new Pair<SqlExpression, IEnumerable<QueryParameterBinding>>(
         processor.Translate(), processor.GetBindings());
       return result;

Orm/Xtensive.Orm/Orm/Providers/SqlCompiler.cs

@@ -111,7 +111,7 @@ protected override SqlProvider VisitCalculate(CalculateProvider provider)
       var sourceColumns = ExtractColumnExpressions(sqlSelect);
       var allBindings = EnumerableUtils<QueryParameterBinding>.Empty;
       foreach (var column in provider.CalculatedColumns) {
-        var result = ProcessExpression(column.Expression, sourceColumns);
+        var result = ProcessExpression(column.Expression, true, sourceColumns);
         var predicate = result.First;
         var bindings = result.Second;
         if (column.Type.StripNullable()==typeof (bool))
@@ -150,7 +150,7 @@ protected override SqlProvider VisitFilter(FilterProvider provider)
       var query = ExtractSqlSelect(provider, source);
 
       var sourceColumns = ExtractColumnExpressions(query);
-      var result = ProcessExpression(provider.Predicate, sourceColumns);
+      var result = ProcessExpression(provider.Predicate, true, sourceColumns);
       var predicate = result.First;
       var bindings = result.Second;
 
@@ -254,7 +254,7 @@ protected override SqlProvider VisitPredicateJoin(PredicateJoinProvider provider
 
       var joinType = provider.JoinType==JoinType.LeftOuter ? SqlJoinType.LeftOuterJoin : SqlJoinType.InnerJoin;
 
-      var result = ProcessExpression(provider.Predicate, leftExpressions, rightExpressions);
+      var result = ProcessExpression(provider.Predicate, false, leftExpressions, rightExpressions);
       var joinExpression = result.First;
       var bindings = result.Second;