ExpressionProcessor supports force use of SqlCase in some cases

Author: alex-kulakov

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

@@ -1,4 +1,4 @@
-// Copyright (C) 2008-2021 Xtensive LLC.
+// Copyright (C) 2008-2024 Xtensive LLC.
 // This code is distributed under MIT license terms.
 // See the License.txt file in the project root for more information.
 // Created by: Alexey Kochetov
@@ -42,6 +42,7 @@ private readonly Dictionary<QueryParameterIdentity, QueryParameterBinding> bindi
     private readonly List<QueryParameterBinding> otherBindings = new List<QueryParameterBinding>();
 
     private readonly bool fixBooleanExpressions;
+    private readonly bool preferCaseOverVariant;
     private readonly bool emptyStringIsNull;
     private readonly bool dateTimeEmulation;
     private readonly bool dateTimeOffsetEmulation;
@@ -332,9 +333,9 @@ protected override SqlExpression VisitConditional(ConditionalExpression expressi
       var boolCheck = fixBooleanExpressions
         ? booleanExpressionConverter.BooleanToInt(check)
         : check;
-      //var varCheck = boolCheck as SqlVariant;
-      //if (!varCheck.IsNullReference())
-      //  return SqlDml.Variant(varCheck.Id, ifFalse, ifTrue);
+      var varCheck = boolCheck as SqlVariant;
+      if (!preferCaseOverVariant && !varCheck.IsNullReference())
+        return SqlDml.Variant(varCheck.Id, ifFalse, ifTrue);
       var @case = SqlDml.Case();
       if (fixBooleanExpressions && IsBooleanExpression(expression)) {
         @case[check] = booleanExpressionConverter.BooleanToInt(ifTrue);
@@ -464,7 +465,7 @@ private SqlExpression TryUnwrapEnum(SqlContainer container)
     // Constructors
 
     public ExpressionProcessor(
-      LambdaExpression lambda, HandlerAccessor handlers, SqlCompiler compiler, params IReadOnlyList<SqlExpression>[] sourceColumns)
+      LambdaExpression lambda, HandlerAccessor handlers, SqlCompiler compiler, bool preferCaseOverVariant, params IReadOnlyList<SqlExpression>[] sourceColumns)
     {
       ArgumentValidator.EnsureArgumentNotNull(lambda, "lambda");
       ArgumentValidator.EnsureArgumentNotNull(handlers, "handlers");
@@ -473,6 +474,7 @@ public ExpressionProcessor(
       this.compiler = compiler; // This might be null, check before use!
       this.lambda = lambda;
       this.sourceColumns = sourceColumns;
+      this.preferCaseOverVariant = preferCaseOverVariant;
 
       providerInfo = handlers.ProviderInfo;
       driver = handlers.StorageDriver;

Orm/Xtensive.Orm/Orm/Providers/PartialIndexFilterCompiler.cs

@@ -24,7 +24,7 @@ public string Compile(HandlerAccessor handlers, IndexInfo index)
         .Cast<SqlExpression>()
         .ToList();
 
-      var processor = new ExpressionProcessor(index.Filter.Expression, handlers, null, columns);
+      var processor = new ExpressionProcessor(filter.Expression, handlers, null, true, columns);
       var fragment = SqlDml.Fragment(processor.Translate());
       var result = handlers.StorageDriver.Compile(fragment).GetCommandText();
       return result;

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

@@ -1,4 +1,4 @@
-// Copyright (C) 2009-2020 Xtensive LLC.
+// Copyright (C) 2009-2024 Xtensive LLC.
 // This code is distributed under MIT license terms.
 // See the License.txt file in the project root for more information.
 // Created by: Denis Krjuchkov
@@ -63,7 +63,7 @@ protected SqlProvider CreateProvider(SqlSelect statement, IEnumerable<QueryParam
     protected Pair<SqlExpression, IEnumerable<QueryParameterBinding>> ProcessExpression(LambdaExpression le,
       params IReadOnlyList<SqlExpression>[] sourceColumns)
     {
-      var processor = new ExpressionProcessor(le, Handlers, this, sourceColumns);
+      var processor = new ExpressionProcessor(le, Handlers, this, (Owner ?? RootProvider).Type == ProviderType.Sort, sourceColumns);
       var result = new Pair<SqlExpression, IEnumerable<QueryParameterBinding>>(
         processor.Translate(), processor.GetBindings());
       return result;