Persist sequence of SqlPersistTask is now IReadOnlyCollection

This allow to have Count of processible requests in CommandFactory.
Current API won't be hurt - new ctors provided and readonly field
extends functionality so it is not a breaking change.
True sequence is List<T> anyway.

Author: alex-kulakov

Orm/Xtensive.Orm/Orm/Providers/CommandProcessing/CommandFactory.cs

@@ -45,7 +45,7 @@ public virtual IEnumerable<CommandPart> CreatePersistParts(SqlPersistTask task,
       ArgumentValidator.EnsureArgumentNotNull(task, "task");
       ArgumentValidator.EnsureArgumentNotNullOrEmpty(parameterNamePrefix, "parameterNamePrefix");
 
-      var result = new List<CommandPart>();
+      var result = new List<CommandPart>(task.RequestSequence.Count);
       int parameterIndex = 0;
       foreach (var request in task.RequestSequence) {
         var tuple = task.Tuple;

Orm/Xtensive.Orm/Orm/Providers/CommandProcessing/SqlPersistTask.cs

@@ -4,7 +4,9 @@
 // Created by: Denis Krjuchkov
 // Created:    2009.08.21
 
+using System;
 using System.Collections.Generic;
+using System.Linq;
 using Xtensive.Collections;
 using Xtensive.Tuples;
 using Tuple = Xtensive.Tuples.Tuple;
@@ -24,7 +26,7 @@ public sealed class SqlPersistTask : SqlTask
     /// <summary>
     /// Requests to execute.
     /// </summary>
-    public readonly IEnumerable<PersistRequest> RequestSequence;
+    public readonly IReadOnlyCollection<PersistRequest> RequestSequence;
 
     /// <summary>
     /// A tuple that stores changed column values.
@@ -52,18 +54,30 @@ public override void ProcessWith(ISqlTaskProcessor processor, CommandProcessorCo
 
     public SqlPersistTask(PersistRequest request, Tuple tuple)
     {
-      RequestSequence = EnumerableUtils.One(request);
+      RequestSequence = new PersistRequest[1] { request };
       Tuple = tuple;
     }
 
+    [Obsolete]
     public SqlPersistTask(Key key, IEnumerable<PersistRequest> requestSequence, Tuple tuple)
+      : this(key, (requestSequence as IReadOnlyCollection<PersistRequest>)?? requestSequence.ToList(), tuple)
+    {
+    }
+
+    [Obsolete]
+    public SqlPersistTask(Key key, IEnumerable<PersistRequest> requestSequence, Tuple tuple, Tuple originalTuple, bool validateRowCount)
+      : this(key, (requestSequence as IReadOnlyCollection<PersistRequest>) ?? requestSequence.ToList(), tuple, originalTuple, validateRowCount)
+    {
+    }
+
+    public SqlPersistTask(Key key, IReadOnlyCollection<PersistRequest> requestSequence, Tuple tuple)
     {
       EntityKey = key;
       RequestSequence = requestSequence;
       Tuple = tuple;
     }
 
-    public SqlPersistTask(Key key, IEnumerable<PersistRequest> requestSequence, Tuple tuple, Tuple originalTuple, bool validateRowCount)
+    public SqlPersistTask(Key key, IReadOnlyCollection<PersistRequest> requestSequence, Tuple tuple, Tuple originalTuple, bool validateRowCount)
     {
       EntityKey = key;
       RequestSequence = requestSequence;

Orm/Xtensive.Orm/Orm/Providers/Persister.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
@@ -93,10 +93,10 @@ private SqlPersistTask CreateRemoveTask(PersistAction action, bool validateVersi
       }
     }
 
-    private ICollection<PersistRequest> GetOrBuildRequest(StorageNode node, PersistRequestBuilderTask task)
+    private IReadOnlyCollection<PersistRequest> GetOrBuildRequest(StorageNode node, PersistRequestBuilderTask task)
     {
       var cache = node.PersistRequestCache;
-      ICollection<PersistRequest> result;
+      IReadOnlyCollection<PersistRequest> result;
       if (cache.TryGetValue(task, out result))
         return result;
       result = requestBuilder.Build(node, task);

Orm/Xtensive.Orm/Orm/Providers/Requests/PersistRequestBuilder.cs

@@ -23,7 +23,7 @@ public class PersistRequestBuilder : DomainBoundHandler
     private ProviderInfo providerInfo;
     private StorageDriver driver;
 
-    internal ICollection<PersistRequest> Build(StorageNode node, PersistRequestBuilderTask task)
+    internal IReadOnlyCollection<PersistRequest> Build(StorageNode node, PersistRequestBuilderTask task)
     {
       var context = new PersistRequestBuilderContext(task, node.Mapping, node.Configuration);
       List<PersistRequest> result;

Orm/Xtensive.Orm/Orm/StorageNode.cs

@@ -48,7 +48,7 @@ public sealed class StorageNode : ISessionSource
 
     internal ConcurrentDictionary<SequenceInfo, object> KeySequencesCache { get; private set; }
 
-    internal ConcurrentDictionary<PersistRequestBuilderTask, ICollection<PersistRequest>> PersistRequestCache { get; private set; }
+    internal ConcurrentDictionary<PersistRequestBuilderTask, IReadOnlyCollection<PersistRequest>> PersistRequestCache { get; private set; }
 
     /// <inheritdoc/>
     public Session OpenSession()
@@ -123,7 +123,7 @@ internal StorageNode(Domain domain, NodeConfiguration configuration, ModelMappin
       TypeIdRegistry = typeIdRegistry;
 
       KeySequencesCache = new ConcurrentDictionary<SequenceInfo, object>();
-      PersistRequestCache = new ConcurrentDictionary<PersistRequestBuilderTask, ICollection<PersistRequest>>();
+      PersistRequestCache = new ConcurrentDictionary<PersistRequestBuilderTask, IReadOnlyCollection<PersistRequest>>();
       InternalQueryCache = new ConcurrentDictionary<object, object>();
     }
   }