diff --git a/Orm/Xtensive.Orm.Firebird/Orm.Providers.Firebird/SqlCompiler.cs b/Orm/Xtensive.Orm.Firebird/Orm.Providers.Firebird/SqlCompiler.cs
index 26c8cebf19..0426acc607 100644
--- a/Orm/Xtensive.Orm.Firebird/Orm.Providers.Firebird/SqlCompiler.cs
+++ b/Orm/Xtensive.Orm.Firebird/Orm.Providers.Firebird/SqlCompiler.cs
@@ -8,13 +8,6 @@
 
 namespace Xtensive.Orm.Providers.Firebird
 {
-  internal class SqlCompiler : Providers.SqlCompiler
-  {
-    // Constructors
-
-    public SqlCompiler(HandlerAccessor handlers, CompilerConfiguration configuration)
-      : base(handlers, configuration)
-    {
-    }
-  }
-}
\ No newline at end of file
+  internal class SqlCompiler(HandlerAccessor handlers, in CompilerConfiguration configuration)
+    : Providers.SqlCompiler(handlers, configuration);
+}
diff --git a/Orm/Xtensive.Orm.MySql/Orm.Providers.MySql/SqlCompiler.cs b/Orm/Xtensive.Orm.MySql/Orm.Providers.MySql/SqlCompiler.cs
index e8cb5d4c9b..e8a3ec49fa 100644
--- a/Orm/Xtensive.Orm.MySql/Orm.Providers.MySql/SqlCompiler.cs
+++ b/Orm/Xtensive.Orm.MySql/Orm.Providers.MySql/SqlCompiler.cs
@@ -9,13 +9,6 @@
 
 namespace Xtensive.Orm.Providers.MySql
 {
-  internal class SqlCompiler : Providers.SqlCompiler
-  {
-    // Constructors
-    
-    public SqlCompiler(HandlerAccessor handlers, CompilerConfiguration configuration)
-      : base(handlers, configuration)
-    {
-    }
-  }
-}
\ No newline at end of file
+  internal class SqlCompiler(HandlerAccessor handlers, in CompilerConfiguration configuration)
+    : Providers.SqlCompiler(handlers, configuration);
+}
diff --git a/Orm/Xtensive.Orm.Oracle/Orm.Providers.Oracle/SqlCompiler.cs b/Orm/Xtensive.Orm.Oracle/Orm.Providers.Oracle/SqlCompiler.cs
index 923c26dfb4..b5f149924d 100644
--- a/Orm/Xtensive.Orm.Oracle/Orm.Providers.Oracle/SqlCompiler.cs
+++ b/Orm/Xtensive.Orm.Oracle/Orm.Providers.Oracle/SqlCompiler.cs
@@ -37,9 +37,9 @@ protected override SqlExpression ProcessAggregate(SqlProvider source, IReadOnlyL
 
     // Constructors
     
-    public SqlCompiler(HandlerAccessor handlers, CompilerConfiguration configuration)
+    public SqlCompiler(HandlerAccessor handlers, in CompilerConfiguration configuration)
       : base(handlers, configuration)
     {
     }
   }
-}
\ No newline at end of file
+}
diff --git a/Orm/Xtensive.Orm.PostgreSql/Orm.Providers.PostgreSql/DomainHandler.cs b/Orm/Xtensive.Orm.PostgreSql/Orm.Providers.PostgreSql/DomainHandler.cs
index 27945b097a..6e8bd7a14f 100644
--- a/Orm/Xtensive.Orm.PostgreSql/Orm.Providers.PostgreSql/DomainHandler.cs
+++ b/Orm/Xtensive.Orm.PostgreSql/Orm.Providers.PostgreSql/DomainHandler.cs
@@ -35,4 +35,4 @@ protected override IEnumerable<Type> GetProviderCompilerContainers()
         });
     }
   }
-}
\ No newline at end of file
+}
diff --git a/Orm/Xtensive.Orm.PostgreSql/Orm.Providers.PostgreSql/SqlCompiler.cs b/Orm/Xtensive.Orm.PostgreSql/Orm.Providers.PostgreSql/SqlCompiler.cs
index 1f7f9e0d2f..094eb81188 100644
--- a/Orm/Xtensive.Orm.PostgreSql/Orm.Providers.PostgreSql/SqlCompiler.cs
+++ b/Orm/Xtensive.Orm.PostgreSql/Orm.Providers.PostgreSql/SqlCompiler.cs
@@ -62,7 +62,7 @@ protected override SqlExpression ProcessAggregate(SqlProvider source, IReadOnlyL
       return result;
     }
 
-    public SqlCompiler(HandlerAccessor handlers, CompilerConfiguration configuration)
+    public SqlCompiler(HandlerAccessor handlers, in CompilerConfiguration configuration)
       : base(handlers, configuration)
     {
     }
diff --git a/Orm/Xtensive.Orm.SqlServer/Orm.Providers.SqlServer/DomainHandler.cs b/Orm/Xtensive.Orm.SqlServer/Orm.Providers.SqlServer/DomainHandler.cs
index 30a34371e8..21407bad60 100644
--- a/Orm/Xtensive.Orm.SqlServer/Orm.Providers.SqlServer/DomainHandler.cs
+++ b/Orm/Xtensive.Orm.SqlServer/Orm.Providers.SqlServer/DomainHandler.cs
@@ -17,10 +17,7 @@ namespace Xtensive.Orm.Providers.SqlServer
   public class DomainHandler : Providers.DomainHandler
   {
     /// <inheritdoc/>
-    protected override ICompiler CreateCompiler(CompilerConfiguration configuration)
-    {
-      return new SqlCompiler(Handlers, configuration);
-    }
+    protected override ICompiler CreateCompiler(CompilerConfiguration configuration) => new SqlCompiler(Handlers, configuration);
 
     /// <inheritdoc/>
     protected override SearchConditionCompiler CreateSearchConditionVisitor()
@@ -30,4 +27,4 @@ protected override SearchConditionCompiler CreateSearchConditionVisitor()
       return new SearchConditionCompilerV11();
     }
   }
-}
\ No newline at end of file
+}
diff --git a/Orm/Xtensive.Orm.SqlServer/Orm.Providers.SqlServer/SqlCompiler.cs b/Orm/Xtensive.Orm.SqlServer/Orm.Providers.SqlServer/SqlCompiler.cs
index d02e718903..f4111d5ca1 100644
--- a/Orm/Xtensive.Orm.SqlServer/Orm.Providers.SqlServer/SqlCompiler.cs
+++ b/Orm/Xtensive.Orm.SqlServer/Orm.Providers.SqlServer/SqlCompiler.cs
@@ -15,7 +15,7 @@
 
 namespace Xtensive.Orm.Providers.SqlServer
 {
-  internal class SqlCompiler : Providers.SqlCompiler
+  internal class SqlCompiler(HandlerAccessor handlers, in CompilerConfiguration configuration) : Providers.SqlCompiler(handlers, configuration)
   {
     private static readonly Type ByteType = typeof(byte);
     private static readonly Type Int16Type = typeof(short);
@@ -149,12 +149,5 @@ private bool ShouldCastDueType(Type type)
         || type == DecimalType
         || type == FloatType;
     }
-
-    // Constructors
-
-    public SqlCompiler(HandlerAccessor handlers, CompilerConfiguration configuration)
-      : base(handlers, configuration)
-    {
-    }
   }
 }
diff --git a/Orm/Xtensive.Orm.SqlServer/Sql.Drivers.SqlServer/v09/ColumnResolver.cs b/Orm/Xtensive.Orm.SqlServer/Sql.Drivers.SqlServer/v09/ColumnResolver.cs
index 61f10b951e..39d1eed9bb 100644
--- a/Orm/Xtensive.Orm.SqlServer/Sql.Drivers.SqlServer/v09/ColumnResolver.cs
+++ b/Orm/Xtensive.Orm.SqlServer/Sql.Drivers.SqlServer/v09/ColumnResolver.cs
@@ -4,59 +4,35 @@
 // Created by: Dmitri Maximov
 // Created:    2009.08.12
 
-using System;
-using System.Collections.Generic;
-using System.Linq;
 using Xtensive.Sql.Model;
 
 namespace Xtensive.Sql.Drivers.SqlServer.v09
 {
-  internal sealed class ColumnResolver
+  internal sealed class ColumnResolver(DataTable table)
   {
-    public DataTable Table;
-    private List<ColumnIndexMapping> columnMappings;
-
-    private class ColumnIndexMapping
-    {
-      public readonly int DbIndex;
-      public readonly int ModelIndex;
-
-      public ColumnIndexMapping(int dbIndex, int modelIndex)
-      {
-        DbIndex = dbIndex;
-        ModelIndex = modelIndex;
-      }
-    }
+    private readonly record struct ColumnIndexMapping(int DbIndex, int ModelIndex, bool IsValid);
 
-    public void RegisterColumnMapping(int dbIndex, int modelIndex)
-    {
-      if (columnMappings == null)
-        columnMappings = new List<ColumnIndexMapping>(1);
+    public DataTable Table = table;
+    private List<ColumnIndexMapping> columnMappings;
 
-      columnMappings.Add(new ColumnIndexMapping(dbIndex, modelIndex));
-    }
+    public void RegisterColumnMapping(int dbIndex, int modelIndex) =>
+      (columnMappings ??= new(1)).Add(new ColumnIndexMapping(dbIndex, modelIndex, true));
 
     public DataTableColumn GetColumn(int dbIndex)
     {
       int modelIndex = dbIndex-1;
-      var view = Table as View;
-      if (view != null)
+      if (Table is View view)
         return view.ViewColumns[modelIndex];
 
       var table = (Table)Table;
       if (columnMappings == null)
         return table.TableColumns[modelIndex];
 
-      var mapping = columnMappings.Where(item => item.DbIndex==dbIndex).FirstOrDefault();
-      if (mapping != null)
+      var mapping = columnMappings.FirstOrDefault(item => item.DbIndex==dbIndex);
+      if (mapping != default)
         return table.TableColumns[mapping.ModelIndex];
 
       throw new ArgumentOutOfRangeException("dbIndex");
     }
-
-    public ColumnResolver(DataTable table)
-    {
-      Table = table;
-    }
   }
-}
\ No newline at end of file
+}
diff --git a/Orm/Xtensive.Orm.Sqlite/Orm.Providers.Sqlite/SqlCompiler.cs b/Orm/Xtensive.Orm.Sqlite/Orm.Providers.Sqlite/SqlCompiler.cs
index 6d886b74fe..4c40025a10 100644
--- a/Orm/Xtensive.Orm.Sqlite/Orm.Providers.Sqlite/SqlCompiler.cs
+++ b/Orm/Xtensive.Orm.Sqlite/Orm.Providers.Sqlite/SqlCompiler.cs
@@ -8,14 +8,6 @@
 
 namespace Xtensive.Orm.Providers.Sqlite
 {
-  internal class SqlCompiler : Providers.SqlCompiler
-  {
-
-    // Constructors
-    
-    public SqlCompiler(HandlerAccessor handlers, CompilerConfiguration configuration)
-      : base(handlers, configuration)
-    {
-    }
-  }
-}
\ No newline at end of file
+  internal class SqlCompiler(HandlerAccessor handlers, in CompilerConfiguration configuration)
+    : Providers.SqlCompiler(handlers, configuration);
+}
diff --git a/Orm/Xtensive.Orm/Core/AliasGenerator.cs b/Orm/Xtensive.Orm/Core/AliasGenerator.cs
index 8550343d47..072b6963a3 100644
--- a/Orm/Xtensive.Orm/Core/AliasGenerator.cs
+++ b/Orm/Xtensive.Orm/Core/AliasGenerator.cs
@@ -12,7 +12,7 @@ namespace Xtensive.Core
   /// Universal alias generator.
   /// </summary>
   [Serializable]
-  public sealed class AliasGenerator
+  public struct AliasGenerator
   {
     /// <summary>
     /// Default alias template. Value is "{0}{1}". Where {0} - template parameter for prefix and {1} - template parameter for suffix.
@@ -93,7 +93,7 @@ public static AliasGenerator Create(string[] overriddenPrefixes, string aliasTem
 
     // Constructors
 
-    private AliasGenerator()
+    public AliasGenerator()
       : this (DefaultAliasTemplate)
     {}
 
@@ -111,4 +111,4 @@ private AliasGenerator(string[] prefixes, string aliasTemplate)
       this.aliasTemplate = aliasTemplate;
     }
   }
-}
\ No newline at end of file
+}
diff --git a/Orm/Xtensive.Orm/Orm/Building/Builders/TypeBuilder.cs b/Orm/Xtensive.Orm/Orm/Building/Builders/TypeBuilder.cs
index ceea7fef93..b66a9bdf2a 100644
--- a/Orm/Xtensive.Orm/Orm/Building/Builders/TypeBuilder.cs
+++ b/Orm/Xtensive.Orm/Orm/Building/Builders/TypeBuilder.cs
@@ -485,18 +485,18 @@ private KeyInfo BuildKeyInfo(TypeInfo root, HierarchyDef hierarchyDef)
       var keyFields = root.Fields
         .Where(static field => field.IsPrimaryKey)
         .OrderBy(static field => field.MappingInfo.Offset)
-        .ToList();
+        .ToArray();
 
       var keyColumns = keyFields
         .Where(static field => field.Column != null)
         .Select(static field => field.Column)
-        .ToList();
+        .ToArray();
 
       var keyTupleDescriptor = TupleDescriptor.Create(
-        keyColumns.Select(static c => c.ValueType).ToArray(keyColumns.Count));
+        keyColumns.Select(static c => c.ValueType).ToArray(keyColumns.Length));
       var typeIdColumnIndex = -1;
       if (hierarchyDef.IncludeTypeId) {
-        for (var i = 0; i < keyColumns.Count; i++) {
+        for (var i = 0; i < keyColumns.Length; i++) {
           if (keyColumns[i].Field.IsTypeId) {
             typeIdColumnIndex = i;
           }
@@ -640,4 +640,4 @@ public TypeBuilder(BuildingContext context)
         .ToDictionary(configuration => context.NameBuilder.BuildKeyGeneratorName(configuration));
     }
   }
-}
\ No newline at end of file
+}
diff --git a/Orm/Xtensive.Orm/Orm/Linq/QueryProvider.cs b/Orm/Xtensive.Orm/Orm/Linq/QueryProvider.cs
index 91575d0e2c..d14d325b5d 100644
--- a/Orm/Xtensive.Orm/Orm/Linq/QueryProvider.cs
+++ b/Orm/Xtensive.Orm/Orm/Linq/QueryProvider.cs
@@ -168,7 +168,7 @@ internal TranslatedQuery Translate(Expression expression) =>
       Translate(expression, Session.CompilationService.CreateConfiguration(Session));
 
     internal TranslatedQuery Translate(Expression expression,
-      CompilerConfiguration compilerConfiguration)
+      in CompilerConfiguration compilerConfiguration)
     {
       try {
         var compiledQueryScope = CompiledQueryProcessingScope.Current;
@@ -189,4 +189,4 @@ internal QueryProvider(Session session)
       Session = session;
     }
   }
-}
\ No newline at end of file
+}
diff --git a/Orm/Xtensive.Orm/Orm/Linq/Rewriters/AggregateOptimizer.cs b/Orm/Xtensive.Orm/Orm/Linq/Rewriters/AggregateOptimizer.cs
index 7b97e45968..ed2944ade2 100644
--- a/Orm/Xtensive.Orm/Orm/Linq/Rewriters/AggregateOptimizer.cs
+++ b/Orm/Xtensive.Orm/Orm/Linq/Rewriters/AggregateOptimizer.cs
@@ -21,6 +21,8 @@ namespace Xtensive.Orm.Linq.Rewriters
 {
   internal sealed class AggregateOptimizer : ExtendedExpressionVisitor
   {
+    private static readonly AggregateOptimizer Instance = new();
+
     private sealed class GroupByItemWrapper<TKey, TElement>
     {
       public TKey Key { get; set; }
@@ -214,7 +216,7 @@ public static Expression Rewrite(Expression expression)
       // This would help Translator to translate GroupBy+Aggregate
       // into single AggregateProvider.
 
-      return new AggregateOptimizer().Visit(expression);
+      return Instance.Visit(expression);
     }
 
     private static void AddGroupByItemWrapper(GroupByQuery groupBy, List<LambdaExpression> elementProjections)
@@ -284,4 +286,4 @@ private AggregateOptimizer()
     {
     }
   }
-}
\ No newline at end of file
+}
diff --git a/Orm/Xtensive.Orm/Orm/Linq/TranslatorContext.cs b/Orm/Xtensive.Orm/Orm/Linq/TranslatorContext.cs
index 4695692b72..9ba72f4208 100644
--- a/Orm/Xtensive.Orm/Orm/Linq/TranslatorContext.cs
+++ b/Orm/Xtensive.Orm/Orm/Linq/TranslatorContext.cs
@@ -25,14 +25,14 @@ namespace Xtensive.Orm.Linq
 {
   internal sealed class TranslatorContext
   {
-    private readonly AliasGenerator resultAliasGenerator;
-    private readonly AliasGenerator columnAliasGenerator;
+    private AliasGenerator resultAliasGenerator = AliasGenerator.Create("#{0}{1}");
+    private AliasGenerator columnAliasGenerator = AliasGenerator.Create(new[] {"c01umn"});
     private readonly Dictionary<ParameterExpression, Parameter<Tuple>> tupleParameters;
     private readonly Dictionary<CompilableProvider, ApplyParameter> applyParameters;
     private readonly Dictionary<ParameterExpression, ItemProjectorExpression> boundItemProjectors;
     private readonly Dictionary<MemberInfo, int> queryReuses;
 
-    public CompilerConfiguration RseCompilerConfiguration { get; }
+    public readonly CompilerConfiguration RseCompilerConfiguration;
 
     public ProviderInfo ProviderInfo { get; }
 
@@ -124,11 +124,7 @@ public ItemProjectorExpression GetBoundItemProjector(ParameterExpression paramet
       return result;
     }
 
-    public void RegisterPossibleQueryReuse(MemberInfo memberInfo)
-    {
-      if (!queryReuses.ContainsKey(memberInfo))
-        queryReuses.Add(memberInfo, 0);
-    }
+    public void RegisterPossibleQueryReuse(MemberInfo memberInfo) => queryReuses.TryAdd(memberInfo, 0);
 
     public bool CheckIfQueryReusePossible(MemberInfo memberInfo)
     {
@@ -148,11 +144,10 @@ private Expression ApplyPreprocessor(IQueryPreprocessor preprocessor, Session se
 
     // Constructors
 
-    public TranslatorContext(Session session, CompilerConfiguration rseCompilerConfiguration, Expression query,
+    public TranslatorContext(Session session, in CompilerConfiguration rseCompilerConfiguration, Expression query,
       CompiledQueryProcessingScope compiledQueryScope)
     {
       ArgumentNullException.ThrowIfNull(session);
-      ArgumentNullException.ThrowIfNull(rseCompilerConfiguration);
       ArgumentNullException.ThrowIfNull(query);
 
       Domain = session.Domain;
@@ -173,8 +168,6 @@ public TranslatorContext(Session session, CompilerConfiguration rseCompilerConfi
       query = PersistentIndexerRewriter.Rewrite(query, this);
       Query = query;
 
-      resultAliasGenerator = AliasGenerator.Create("#{0}{1}");
-      columnAliasGenerator = AliasGenerator.Create(new[] {"c01umn"});
       CustomCompilerProvider = Domain.Handler.GetMemberCompilerProvider<Expression>();
       Model = Domain.Model;
       TypeIdRegistry = session.StorageNode.TypeIdRegistry;
diff --git a/Orm/Xtensive.Orm/Orm/Providers/CompilationService.cs b/Orm/Xtensive.Orm/Orm/Providers/CompilationService.cs
index ac41c134e3..906bb52e73 100644
--- a/Orm/Xtensive.Orm/Orm/Providers/CompilationService.cs
+++ b/Orm/Xtensive.Orm/Orm/Providers/CompilationService.cs
@@ -14,19 +14,20 @@ namespace Xtensive.Orm.Providers
   /// <summary>
   /// <see cref="CompilableProvider"/> compilation service.
   /// </summary>
-  public sealed class CompilationService
+  public readonly struct CompilationService
   {
     private readonly Func<CompilerConfiguration, ICompiler> compilerProvider;
     private readonly Func<CompilerConfiguration, IPreCompiler> preCompilerProvider;
     private readonly Func<CompilerConfiguration, ICompiler, IPostCompiler> postCompilerProvider;
 
     public CompilerConfiguration CreateConfiguration(Session session) =>
-      new() {
-        StorageNode = session.StorageNode,
-        Tags = session.Tags,
+      new(
+        PrepareRequest: true,
+        StorageNode: session.StorageNode,
+        Tags: session.Tags,
         // prefer constants during upgrade process
-        PreferTypeIdAsParameter = !session.Name.Equals(WellKnown.Sessions.System) && session.Domain.Configuration.PreferTypeIdsAsQueryParameters
-      };
+        PreferTypeIdAsParameter: !session.Name.Equals(WellKnown.Sessions.System) && session.Domain.Configuration.PreferTypeIdsAsQueryParameters
+      );
 
     public ExecutableProvider Compile(CompilableProvider provider, CompilerConfiguration configuration)
     {
@@ -58,12 +59,12 @@ public CompilationService(
       Func<CompilerConfiguration, ICompiler, IPostCompiler> postCompilerProvider)
     {
       ArgumentNullException.ThrowIfNull(compilerProvider);
-      ArgumentNullException.ThrowIfNull(compilerProvider, "preCompilerProvider");
-      ArgumentNullException.ThrowIfNull(compilerProvider, "postCompilerProvider");
+      ArgumentNullException.ThrowIfNull(preCompilerProvider);
+      ArgumentNullException.ThrowIfNull(postCompilerProvider);
 
       this.compilerProvider = compilerProvider;
       this.preCompilerProvider = preCompilerProvider;
       this.postCompilerProvider = postCompilerProvider;
     }
   }
-}
\ No newline at end of file
+}
diff --git a/Orm/Xtensive.Orm/Orm/Providers/CompilerConfiguration.cs b/Orm/Xtensive.Orm/Orm/Providers/CompilerConfiguration.cs
index 46c2649f3a..2686ab7966 100644
--- a/Orm/Xtensive.Orm/Orm/Providers/CompilerConfiguration.cs
+++ b/Orm/Xtensive.Orm/Orm/Providers/CompilerConfiguration.cs
@@ -8,20 +8,11 @@
 
 namespace Xtensive.Orm.Providers
 {
-  public sealed class CompilerConfiguration
-  {
-    public bool PrepareRequest { get; set; }
-    public bool PreferTypeIdAsParameter { get; set; }
-    public IReadOnlyList<string> Tags { get; init; }
-
-    internal StorageNode StorageNode { get; set; }
-
-
-    // Constructors
-
-    public CompilerConfiguration()
-    {
-      PrepareRequest = true;
-    }
-  }
-}
\ No newline at end of file
+  public readonly record struct CompilerConfiguration
+  (
+    bool PrepareRequest,
+    bool PreferTypeIdAsParameter,
+    IReadOnlyList<string> Tags,
+    StorageNode StorageNode
+  );
+}
diff --git a/Orm/Xtensive.Orm/Orm/Providers/DomainHandler.cs b/Orm/Xtensive.Orm/Orm/Providers/DomainHandler.cs
index 6e7824d522..2f716f056f 100644
--- a/Orm/Xtensive.Orm/Orm/Providers/DomainHandler.cs
+++ b/Orm/Xtensive.Orm/Orm/Providers/DomainHandler.cs
@@ -109,13 +109,10 @@ protected virtual IPreCompiler CreatePreCompiler(CompilerConfiguration configura
     /// <param name="configuration">Compiler configuration to use.</param>
     /// <param name="compiler">Currently used compiler instance.</param>
     /// <returns>A new post-compiler.</returns>
-    protected virtual IPostCompiler CreatePostCompiler(CompilerConfiguration configuration, ICompiler compiler)
-    {
-      var result = new CompositePostCompiler(new SqlSelectCorrector(Handlers.ProviderInfo));
-      if (configuration.PrepareRequest)
-        result.Items.Add(new SqlProviderPreparer(Handlers));
-      return result;
-    }
+    protected virtual IPostCompiler CreatePostCompiler(CompilerConfiguration configuration, ICompiler compiler) =>
+      configuration.PrepareRequest
+        ? new CompositePostCompiler([new SqlSelectCorrector(Handlers.ProviderInfo), new SqlProviderPreparer(Handlers)])
+        : new CompositePostCompiler([new SqlSelectCorrector(Handlers.ProviderInfo)]);
 
     /// <summary>
     /// Gets compiler containers specific to current storage provider.
@@ -214,4 +211,4 @@ public void InitializeServices()
       BuildQueryPreprocessors();
     }
   }
-}
\ No newline at end of file
+}
diff --git a/Orm/Xtensive.Orm/Orm/Providers/SqlCompiler.cs b/Orm/Xtensive.Orm/Orm/Providers/SqlCompiler.cs
index 17c02d4b41..3969f90df8 100644
--- a/Orm/Xtensive.Orm/Orm/Providers/SqlCompiler.cs
+++ b/Orm/Xtensive.Orm/Orm/Providers/SqlCompiler.cs
@@ -594,7 +594,7 @@ protected override void Initialize()
     /// <summary>
     /// Initializes a new instance of this class.
     /// </summary>
-    public SqlCompiler(HandlerAccessor handlers, CompilerConfiguration configuration)
+    public SqlCompiler(HandlerAccessor handlers, in CompilerConfiguration configuration)
     {
       Handlers = handlers;
       OuterReferences = new BindingCollection<ApplyParameter, Pair<SqlProvider, bool>>();
diff --git a/Orm/Xtensive.Orm/Orm/Rse/Compilation/CompositePostCompiler.cs b/Orm/Xtensive.Orm/Orm/Rse/Compilation/CompositePostCompiler.cs
index 0c781c76bc..eeb941ceaa 100644
--- a/Orm/Xtensive.Orm/Orm/Rse/Compilation/CompositePostCompiler.cs
+++ b/Orm/Xtensive.Orm/Orm/Rse/Compilation/CompositePostCompiler.cs
@@ -1,4 +1,4 @@
-// Copyright (C) 2012 Xtensive LLC.
+// Copyright (C) 2012 Xtensive LLC.
 // All rights reserved.
 // For conditions of distribution and use, see license.
 // Created by: Denis Krjuchkov
@@ -10,9 +10,9 @@
 
 namespace Xtensive.Orm.Rse.Compilation
 {
-  public class CompositePostCompiler : IPostCompiler
+  public class CompositePostCompiler(IReadOnlyList<IPostCompiler> items) : IPostCompiler
   {
-    public List<IPostCompiler> Items { get; private set; }
+    public IReadOnlyList<IPostCompiler> Items { get; } = items;
 
     public ExecutableProvider Process(ExecutableProvider rootProvider)
     {
@@ -21,13 +21,5 @@ public ExecutableProvider Process(ExecutableProvider rootProvider)
         provider = item.Process(provider);
       return provider;
     }
-
-
-    // Constructors
-
-    public CompositePostCompiler(params IPostCompiler[] postCompilers)
-    {
-      Items = postCompilers.ToList();
-    }
   }
-}
\ No newline at end of file
+}
diff --git a/Orm/Xtensive.Orm/Orm/Services/QueryBuilding/QueryBuilder.cs b/Orm/Xtensive.Orm/Orm/Services/QueryBuilding/QueryBuilder.cs
index 9de43a936d..44d342468e 100644
--- a/Orm/Xtensive.Orm/Orm/Services/QueryBuilding/QueryBuilder.cs
+++ b/Orm/Xtensive.Orm/Orm/Services/QueryBuilding/QueryBuilder.cs
@@ -37,8 +37,7 @@ public QueryTranslationResult TranslateQuery<TResult>(IQueryable<TResult> query)
     {
       ArgumentNullException.ThrowIfNull(query);
 
-      var configuration = Session.CompilationService.CreateConfiguration(Session);
-      configuration.PrepareRequest = false;
+      var configuration = Session.CompilationService.CreateConfiguration(Session) with { PrepareRequest = false };
       var translated = queryProvider.Translate(query.Expression, configuration);
 
       var sqlProvider = translated.DataSource as SqlProvider;
@@ -124,4 +123,4 @@ public QueryBuilder(Session session)
       queryProvider = session.Query.Provider;
     }
   }
-}
\ No newline at end of file
+}
diff --git a/Orm/Xtensive.Orm/Orm/Services/QueryFormatter.cs b/Orm/Xtensive.Orm/Orm/Services/QueryFormatter.cs
index b1ab291957..dbe1c75a78 100644
--- a/Orm/Xtensive.Orm/Orm/Services/QueryFormatter.cs
+++ b/Orm/Xtensive.Orm/Orm/Services/QueryFormatter.cs
@@ -69,8 +69,7 @@ public DbCommand ToDbCommand<T>(IQueryable<T> query)
 
     private CommandPart GetCommandPart<T>(IQueryable<T> query)
     {
-      var compilerConfiguration = Session.CompilationService.CreateConfiguration(Session);
-      compilerConfiguration.PreferTypeIdAsParameter = false;
+      var compilerConfiguration = Session.CompilationService.CreateConfiguration(Session) with { PreferTypeIdAsParameter = false };
 
       var translatedQuery = Session.Query.Provider.Translate(query.Expression, compilerConfiguration);
       var sqlProvider = translatedQuery.DataSource as SqlProvider;
@@ -93,4 +92,4 @@ public QueryFormatter(Session session)
       commandFactory = sqlSessionHandler.CommandFactory;
     }
   }
-}
\ No newline at end of file
+}
diff --git a/Orm/Xtensive.Orm/Orm/Session.cs b/Orm/Xtensive.Orm/Orm/Session.cs
index 2f74feecb2..ba6e710487 100644
--- a/Orm/Xtensive.Orm/Orm/Session.cs
+++ b/Orm/Xtensive.Orm/Orm/Session.cs
@@ -242,7 +242,7 @@ public static Func<Session> Resolver
 
     internal RemovalProcessor RemovalProcessor { get; private set; }
 
-    internal CompilationService CompilationService { get { return Handlers.DomainHandler.CompilationService; } }
+    internal CompilationService CompilationService => Handlers.DomainHandler.CompilationService;
 
     internal IReadOnlyList<string> Tags => tags;
 
@@ -344,10 +344,8 @@ internal StorageNode GetStorageNodeInternal()
       return storageNode;
     }
 
-    internal ExecutableProvider Compile(CompilableProvider provider)
-    {
-      return CompilationService.Compile(provider, CompilationService.CreateConfiguration(this));
-    }
+    internal ExecutableProvider Compile(CompilableProvider provider) =>
+      CompilationService.Compile(provider, CompilationService.CreateConfiguration(this));
 
     internal ExecutableProvider Compile(CompilableProvider provider, CompilerConfiguration configuration)
     {
diff --git a/Orm/Xtensive.Orm/Sql/Model/NodeCollection.cs b/Orm/Xtensive.Orm/Sql/Model/NodeCollection.cs
index bd594c18f2..65d7333a34 100644
--- a/Orm/Xtensive.Orm/Sql/Model/NodeCollection.cs
+++ b/Orm/Xtensive.Orm/Sql/Model/NodeCollection.cs
@@ -34,8 +34,9 @@ public class NodeCollection<TNode>: CollectionBaseSlim<TNode>
     public override void Add(TNode item)
     {
       base.Add(item);
-      if (!string.IsNullOrEmpty(item.GetNameInternal()))
-        nameIndex.Add(item.GetNameInternal(), item);
+      var name = item.GetNameInternal();
+      if (!string.IsNullOrEmpty(name))
+        nameIndex.Add(name, item);
     }
 
     /// <inheritdoc/>
@@ -67,14 +68,9 @@ public override void Clear()
     /// <summary>
     /// Gets the <typeparamref name="TNode"/> at the specified index.
     /// </summary>
-    public TNode this[string index] {
-      get {
-        if (string.IsNullOrEmpty(index))
-          return default(TNode);
-        TNode result;
-        return nameIndex.TryGetValue(index, out result) ? result : default(TNode);
-      }
-    }
+    public TNode this[string index] => string.IsNullOrEmpty(index)
+      ? default
+      : nameIndex.TryGetValue(index, out var result) ? result : default(TNode);
 
 
     // Constructors
@@ -108,4 +104,4 @@ public NodeCollection(int capacity, IEqualityComparer<string> comparer)
       nameIndex = new Dictionary<string, TNode>(capacity, comparer);
     }
   }
-}
\ No newline at end of file
+}