Get rid of custom Copy methods for arrays. Plus this eliminates creation of unnecessary array copies.

# Conflicts:
#	Orm/Xtensive.Orm/Orm/Rse/Providers/Compilable/IncludeProvider.cs

Author: AlexUstinov

Orm/Xtensive.Orm/Collections/ThreadSafeList.cs

@@ -137,7 +137,7 @@ public void SetValue(int index, TItem item)
           length *= 2;
         }
         TItem[] tmp = new TItem[length];
-        implementation.Copy(tmp, 0);
+        implementation.CopyTo(tmp, 0);
         tmp[index] = item;
         Thread.MemoryBarrier(); // Ensures item and tmp are fully written
         implementation = tmp;

Orm/Xtensive.Orm/Comparison/ComparisonRules.cs

@@ -5,9 +5,9 @@
 // Created:    2008.02.04
 
 using System;
+using System.Collections.Generic;
 using System.Diagnostics;
 using System.Text;
-using Xtensive.Collections;
 using Xtensive.Core;
 
 
@@ -142,10 +142,9 @@ public Direction GetDefaultRuleDirection(int index)
     /// Gets a copy of internal array of composite rules
     /// that are used to order composite values.
     /// </summary>
-    public ComparisonRules[] Composite {
-      get {
-        return composite.Copy();
-      }
+    public IReadOnlyList<ComparisonRules> Composite {
+      [DebuggerStepThrough]
+      get => Array.AsReadOnly(composite);
     }
 
     /// <summary>

Orm/Xtensive.Orm/Core/Extensions/ArrayExtensions.cs

@@ -25,10 +25,11 @@ public static class ArrayExtensions
     /// <typeparam name="TItem">The type of array items.</typeparam>
     /// <param name="source">Array to clone.</param>
     /// <returns>An array containing all the items from the <paramref name="source"/>.</returns>
+    [Obsolete]
     public static TItem[] Copy<TItem>(this TItem[] source)
     {
       var items = new TItem[source.Length];
-      source.Copy(items, 0);
+      source.CopyTo(items, 0);
       return items;
     }
 
@@ -43,6 +44,7 @@ public static TItem[] Copy<TItem>(this TItem[] source)
     /// <param name="targetIndex">Index in <paramref name="target"/> array to start from.</param>
     /// <exception cref="ArgumentOutOfRangeException"><paramref name="targetIndex"/> is out of range.</exception>
     /// <exception cref="ArgumentException"><paramref name="target"/> array is too small.</exception>
+    [Obsolete]
     public static void Copy<TItem>(this TItem[] source, TItem[] target, int targetIndex)
     {
       ArgumentValidator.EnsureArgumentNotNull(source, "source");

Orm/Xtensive.Orm/Core/Extensions/ListExtensions.cs

@@ -8,7 +8,6 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
-using Xtensive.Core;
 
 
 namespace Xtensive.Core
@@ -18,6 +17,18 @@ namespace Xtensive.Core
   /// </summary>
   public static class ListExtensions
   {
+    public static int IndexOf<T>(this IReadOnlyList<T> list, T item)
+    {
+      var comparer = EqualityComparer<T>.Default;
+      for (int index = 0, count = list.Count; index < count; index++) {
+        if (comparer.Equals(list[index], item)) {
+          return index;
+        }
+      }
+
+      return -1;
+    }
+
     #region Copy methods
 
     /// <summary>

Orm/Xtensive.Orm/Orm/Internals/Prefetch/EntityGroupTask.cs

@@ -7,7 +7,6 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using Xtensive.Collections;
 using Xtensive.Core;
 using Xtensive.Orm.Model;
 using Xtensive.Orm.Rse;
@@ -167,12 +166,15 @@ private static CompilableProvider CreateRecordSet(object cachingKey)
     {
       var pair = (Pair<object, CacheKey>) cachingKey;
       var selectedColumnIndexes = pair.Second.ColumnIndexes;
-      var keyColumnIndexes = EnumerableUtils.Unfold(0, i => i + 1)
-        .Take(pair.Second.Type.Indexes.PrimaryIndex.KeyColumns.Count).ToArray();
-      var columnCollectionLenght = pair.Second.Type.Indexes.PrimaryIndex.Columns.Count;
+      var keyColumnsCount = pair.Second.Type.Indexes.PrimaryIndex.KeyColumns.Count;
+      var keyColumnIndexes = new int[keyColumnsCount];
+      foreach (var index in Enumerable.Range(0, keyColumnsCount)) {
+        keyColumnIndexes[index] = index;
+      }
+      var columnCollectionLength = pair.Second.Type.Indexes.PrimaryIndex.Columns.Count;
       return pair.Second.Type.Indexes.PrimaryIndex.GetQuery().Include(IncludeAlgorithm.ComplexCondition,
-        true, () => includeParameter.Value, String.Format("includeColumnName-{0}", Guid.NewGuid()),
-        keyColumnIndexes).Filter(t => t.GetValue<bool>(columnCollectionLenght)).Select(selectedColumnIndexes);
+        true, () => includeParameter.Value, $"includeColumnName-{Guid.NewGuid()}",
+        keyColumnIndexes).Filter(t => t.GetValue<bool>(columnCollectionLength)).Select(selectedColumnIndexes);
     }
 
     private void PutLoadedStatesInCache(IEnumerable<Tuple> queryResult, RecordSetReader reader,

Orm/Xtensive.Orm/Orm/Linq/Translator.Queryable.cs

@@ -5,7 +5,6 @@
 // Created:    2009.02.27
 
 using System;
-using System.Collections;
 using System.Collections.Generic;
 using System.Linq;
 using System.Linq.Expressions;
@@ -1306,7 +1305,7 @@ private Expression VisitExistsAsInclude(Expression source, LambdaExpression pred
           predicateLambda.Body, predicateLambda.Parameters[0], filteredTuple, filterColumnCount);
 
         // Mapping from filter data column to filtered column
-        var filteredColumns = Enumerable.Repeat(-1, filterColumnCount).ToArray();
+        var filteredColumns = new int[filterColumnCount];
         for (int i = 0; i < filterColumnCount; i++) {
           var mapping = filteredColumnMappings[i];
           if (mapping.ColumnIndex >= 0)

Orm/Xtensive.Orm/Orm/Rse/Providers/Compilable/IncludeProvider.cs

@@ -8,7 +8,6 @@
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq.Expressions;
-using Xtensive.Collections;
 using Xtensive.Core;
 
 using Xtensive.Tuples;
@@ -27,8 +26,6 @@ namespace Xtensive.Orm.Rse.Providers
   public sealed class IncludeProvider: UnaryProvider,
     IInlinableProvider
   {
-    private readonly int[] filteredColumns;
-
     /// <summary>
     /// Gets a value indicating whether result column should be inlined.
     /// </summary>
@@ -40,18 +37,15 @@ public sealed class IncludeProvider: UnaryProvider,
     public string ResultColumnName { get; private set; }
 
     /// <summary>
-    /// Gets the algorithm that performes filtering.
+    /// Gets the algorithm that performs filtering.
     /// For non-SQL storages value of this field has no effect.
     /// </summary>
     public IncludeAlgorithm Algorithm { get; private set; }
 
     /// <summary>
     /// Gets the filtered columns.
     /// </summary>
-    public int[] FilteredColumns {
-      [DebuggerStepThrough]
-      get { return filteredColumns.Copy(); }
-    }
+    public IReadOnlyList<int> FilteredColumns { [DebuggerStepThrough] get; }
 
     /// <summary>
     /// Gets filter data.
@@ -66,9 +60,13 @@ public int[] FilteredColumns {
     protected override RecordSetHeader BuildHeader()
     {
       var newHeader = Source.Header.Add(new SystemColumn(ResultColumnName, 0, typeof(bool)));
-      var types = FilteredColumns.Select(m => newHeader.Columns[m].Type);
-      FilteredColumnsExtractionTransform = new MapTransform(true, TupleDescriptor.Create(types), FilteredColumns);
-      ResultTransform = new CombineTransform(true, Source.Header.TupleDescriptor, TupleDescriptor.Create(new []{typeof(bool)}));
+      var fieldTypes = new Type[FilteredColumns.Count];
+      for (var index = 0; index < fieldTypes.Length; index++) {
+        fieldTypes[index] = newHeader.Columns[FilteredColumns[index]].Type;
+      }
+      var tupleDescriptor = TupleDescriptor.Create(fieldTypes);
+      FilteredColumnsExtractionTransform = new MapTransform(true, tupleDescriptor, FilteredColumns);
+      ResultTransform = new CombineTransform(true, Source.Header.TupleDescriptor, TupleDescriptor.Create<bool>());
       return newHeader;
     }
 
@@ -85,7 +83,7 @@ protected override RecordSetHeader BuildHeader()
     /// <param name="resultColumnName">A value for <see cref="ResultColumnName"/>.</param>
     /// <param name="filteredColumns">A value for <see cref="FilteredColumns"/>.</param>
     public IncludeProvider(CompilableProvider source, IncludeAlgorithm algorithm, bool isInlined,
-      Expression<Func<IEnumerable<Tuple>>> filterDataSource, string resultColumnName, int[] filteredColumns)
+      Expression<Func<IEnumerable<Tuple>>> filterDataSource, string resultColumnName, IReadOnlyList<int> filteredColumns)
       : base(ProviderType.Include, source)
     {
       ArgumentValidator.EnsureArgumentNotNull(filterDataSource, "filterDataSource");
@@ -95,7 +93,7 @@ public IncludeProvider(CompilableProvider source, IncludeAlgorithm algorithm, bo
       IsInlined = isInlined;
       FilterDataSource = filterDataSource;
       ResultColumnName = resultColumnName;
-      this.filteredColumns = filteredColumns.Copy();
+      FilteredColumns = filteredColumns is int[] columns ? Array.AsReadOnly(columns) : filteredColumns;
       Initialize();
     }
   }

Orm/Xtensive.Orm/Orm/Rse/Providers/Compilable/SelectProvider.cs

@@ -8,11 +8,8 @@
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
-using Xtensive.Collections;
 using Xtensive.Core;
 
-using Xtensive.Orm.Rse.Providers;
-
 namespace Xtensive.Orm.Rse.Providers
 {
   /// <summary>
@@ -21,15 +18,10 @@ namespace Xtensive.Orm.Rse.Providers
   [Serializable]
   public sealed class SelectProvider : UnaryProvider
   {
-    private readonly int[] columnIndexes;
-
     /// <summary>
     /// Indexes of columns that should be selected from the <see cref="UnaryProvider.Source"/>.
     /// </summary>
-    public int[] ColumnIndexes {
-      [DebuggerStepThrough]
-      get { return columnIndexes.Copy(); }
-    }
+    public IReadOnlyList<int> ColumnIndexes { [DebuggerStepThrough] get; }
 
     /// <inheritdoc/>
     protected override RecordSetHeader BuildHeader()
@@ -52,7 +44,17 @@ protected override string ParametersToString()
     public SelectProvider(CompilableProvider provider, int[] columnIndexes)
       : base(ProviderType.Select, provider)
     {
-      this.columnIndexes = columnIndexes;
+      this.ColumnIndexes = Array.AsReadOnly(columnIndexes);
+      Initialize();
+    }
+
+    /// <summary>
+    ///   Initializes a new instance of this class.
+    /// </summary>
+    public SelectProvider(CompilableProvider provider, IReadOnlyList<int> columnIndexes)
+      : base(ProviderType.Select, provider)
+    {
+      this.ColumnIndexes = columnIndexes is int[] indexes  ? indexes : columnIndexes;
       Initialize();
     }
   }

Orm/Xtensive.Orm/Orm/Rse/Transformation/Internals/OrderingRewriter.cs

@@ -71,8 +71,9 @@ protected override Provider VisitSelect(SelectProvider provider)
 
       if (sortOrder.Count > 0) {
         var selectOrdering = new DirectionCollection<int>();
+        var columnIndexes = result.ColumnIndexes;
         foreach (var pair in sortOrder) {
-          var columnIndex = result.ColumnIndexes.IndexOf(pair.Key);
+          var columnIndex = columnIndexes.IndexOf(pair.Key);
           if (columnIndex < 0) {
             if (selectOrdering.Count > 0)
               selectOrdering.Clear();

Orm/Xtensive.Orm/Tuples/Transform/CombineTransform.cs

@@ -8,11 +8,8 @@
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
-using Xtensive.Collections;
 using Xtensive.Core;
 using Xtensive.Reflection;
-using Xtensive.Tuples.Transform;
-
 
 
 namespace Xtensive.Tuples.Transform
@@ -28,10 +25,10 @@ public sealed class CombineTransform : MapTransform
     /// <summary>
     /// Gets tuple descriptors this transform merges.
     /// </summary>
-    public TupleDescriptor[] Sources
+    public IReadOnlyList<TupleDescriptor> Sources
     {
       [DebuggerStepThrough]
-      get { return sources.Copy(); }
+      get => Array.AsReadOnly(sources);
     }
 
     /// <see cref="MapTransform.Apply(TupleTransformType,Tuple,Tuple)" copy="true" />
@@ -84,7 +81,7 @@ public CombineTransform(bool isReadOnly, params TupleDescriptor[] sources)
       }
       this.sources = sources;
       Descriptor = TupleDescriptor.Create(types);
-      Map = map;
+      SetMap(map);
     }
   }
 }