Merge pull request #399 from DataObjects-NET/master-temptablemanager-imps

Small improvements of TemporaryTableManager and TupleDescriptor

Author: alex-kulakov

Orm/Xtensive.Orm/Orm/Providers/TemporaryTables/TemporaryTableManager.cs

@@ -24,8 +24,14 @@ public class TemporaryTableManager : DomainBoundHandler
     private const string TableNamePattern = "Tmp_{0}";
     private const string ColumnNamePattern = "C{0}";
 
-    // Preallocated array of 1 column name
-    private static readonly string[] ColumnNames1 = new[] { string.Format(ColumnNamePattern, 0) };
+    // Preallocated array of 8 column names
+    // to get parts of it
+    private readonly string[] columnNames8 = new[] {
+      string.Format(ColumnNamePattern, 0), string.Format(ColumnNamePattern, 1),
+      string.Format(ColumnNamePattern, 2), string.Format(ColumnNamePattern, 3),
+      string.Format(ColumnNamePattern, 4), string.Format(ColumnNamePattern, 5),
+      string.Format(ColumnNamePattern, 6), string.Format(ColumnNamePattern, 7),
+    };
 
     private TemporaryTableBackEnd backEnd;
     private bool useTruncate;
@@ -42,7 +48,7 @@ public class TemporaryTableManager : DomainBoundHandler
     /// <param name="name">The name of the temporary table.</param>
     /// <param name="source">The source.</param>
     /// <returns>Built descriptor.</returns>
-    public TemporaryTableDescriptor BuildDescriptor(ModelMapping modelMapping, string name, TupleDescriptor source)
+    public TemporaryTableDescriptor BuildDescriptor(ModelMapping modelMapping, string name, in TupleDescriptor source)
     {
       return BuildDescriptor(modelMapping, name, source, null);
     }
@@ -55,7 +61,7 @@ public TemporaryTableDescriptor BuildDescriptor(ModelMapping modelMapping, strin
     /// <param name="source">The source.</param>
     /// <param name="fieldNames">The names of field in temporary table.</param>
     /// <returns>Built descriptor.</returns>
-    public TemporaryTableDescriptor BuildDescriptor(ModelMapping modelMapping, string name, TupleDescriptor source, string[] fieldNames)
+    public TemporaryTableDescriptor BuildDescriptor(ModelMapping modelMapping, string name, in TupleDescriptor source, string[] fieldNames)
     {
       EnsureTemporaryTablesSupported();
 
@@ -70,14 +76,14 @@ public TemporaryTableDescriptor BuildDescriptor(ModelMapping modelMapping, strin
         ? new Collation(schema, modelMapping.TemporaryTableCollation)
         : null;
 
-      fieldNames ??= BuildFieldNames(source);
+      var resultFieldNames = fieldNames ?? BuildFieldNamesAsSegment(source);
 
       var typeMappings = source
         .Select(driver.GetTypeMapping)
         .ToArray();
 
       // table
-      var table = CreateTemporaryTable(schema, name, source, typeMappings, fieldNames, collation);
+      var table = CreateTemporaryTable(schema, name, source, typeMappings, resultFieldNames, collation);
       var tableRef = SqlDml.TableRef(table);
 
       // select statement
@@ -163,16 +169,20 @@ private void EnsureTemporaryTablesSupported()
         throw new NotSupportedException(Strings.ExTemporaryTablesAreNotSupportedByCurrentStorage);
     }
 
-    private string[] BuildFieldNames(in TupleDescriptor source) =>
-      source.Count == 1
-        ? ColumnNames1
+    private ArraySegment<string> BuildFieldNamesAsSegment(TupleDescriptor source)
+    {
+      var count = source.Count;
+      return count <= 8
+        ? new ArraySegment<string>(columnNames8, 0, count)
         : Enumerable.Range(0, source.Count)
           .Select(i => string.Format(ColumnNamePattern, i))
           .ToArray();
+    }
 
-    private Table CreateTemporaryTable(Schema schema, string name, TupleDescriptor source, TypeMapping[] typeMappings, string[] fieldNames, Collation collation)
+    private Table CreateTemporaryTable(Schema schema,
+      string tempTableName, in TupleDescriptor source, TypeMapping[] typeMappings, ArraySegment<string> fieldNames, Collation collation)
     {
-      var tableName = Handlers.NameBuilder.ApplyNamingRules(string.Format(TableNamePattern, name));
+      var tableName = Handlers.NameBuilder.ApplyNamingRules(string.Format(TableNamePattern, tempTableName));
       var table = backEnd.CreateTemporaryTable(schema, tableName);
 
       if (source.Count > 0) {

Orm/Xtensive.Orm/Tuples/TupleDescriptor.cs

@@ -25,7 +25,7 @@ namespace Xtensive.Tuples
   [Serializable]
   public readonly struct TupleDescriptor : IEquatable<TupleDescriptor>, IReadOnlyList<Type>, ISerializable
   {
-    private static readonly TupleDescriptor EmptyDescriptor = new TupleDescriptor(Array.Empty<Type>());
+    public static readonly TupleDescriptor Empty = new TupleDescriptor(Array.Empty<Type>());
 
     internal readonly int ValuesLength;
     internal readonly int ObjectsLength;
@@ -36,18 +36,6 @@ namespace Xtensive.Tuples
     [field: NonSerialized]
     private Type[] FieldTypes { get; }
 
-    private int FieldCount => FieldTypes.Length;
-
-    /// <summary>
-    /// Gets the empty tuple descriptor.
-    /// </summary>
-    /// <value>The empty tuple descriptor.</value>
-    public static TupleDescriptor Empty
-    {
-      [DebuggerStepThrough]
-      get => EmptyDescriptor;
-    }
-
     #region IList members
 
     /// <inheritdoc/>
@@ -61,13 +49,13 @@ public Type this[int fieldIndex]
     public int Count
     {
       [DebuggerStepThrough]
-      get => FieldCount;
+      get => FieldTypes.Length;
     }
 
     /// <inheritdoc/>
     public IEnumerator<Type> GetEnumerator()
     {
-      for (var index = 0; index < FieldCount; index++) {
+      for (int index = 0, count = Count; index < count; index++) {
         yield return FieldTypes[index];
       }
     }
@@ -89,11 +77,11 @@ public bool Equals(TupleDescriptor other)
       if (FieldTypes == null) {
         return other.FieldTypes == null;
       }
-      if (other.FieldTypes == null || FieldCount != other.FieldCount) {
+      if (other.FieldTypes == null || Count != other.Count) {
         return false;
       }
 
-      for (int i = 0; i < FieldCount; i++) {
+      for (int i = 0, count = Count; i < count; i++) {
         if (FieldTypes[i] != other.FieldTypes[i]) {
           return false;
         }
@@ -108,35 +96,42 @@ public override bool Equals(object obj) =>
     /// <inheritdoc/>
     public override int GetHashCode()
     {
-      int result = FieldCount;
-      for (int i = 0; i < FieldCount; i++)
+      int result = Count;
+      for (int i = 0, count = Count; i < count; i++)
         result = unchecked (FieldTypes[i].GetHashCode() + 29 * result);
       return result;
     }
 
-    public static bool operator ==(in TupleDescriptor left, in TupleDescriptor right) => left.Equals(right);
-    public static bool operator !=(in TupleDescriptor left, in TupleDescriptor right) => !(left == right);
+    public static bool operator ==(in TupleDescriptor left, in TupleDescriptor right)
+    {
+      return left.Equals(right);
+    }
+
+    public static bool operator !=(in TupleDescriptor left, in TupleDescriptor right)
+    {
+      return !(left == right);
+    }
 
     #endregion
 
     public void GetObjectData(SerializationInfo info, StreamingContext context)
     {
-      info.AddValue("ValuesLength", ValuesLength);
-      info.AddValue("ObjectsLength", ObjectsLength);
+      info.AddValue(nameof(ValuesLength), ValuesLength);
+      info.AddValue(nameof(ObjectsLength), ObjectsLength);
 
       var typeNames = new string[FieldTypes.Length];
       for (var i = 0; i < typeNames.Length; i++)
         typeNames[i] = FieldTypes[i].ToSerializableForm();
 
-      info.AddValue("FieldTypes", typeNames);
-      info.AddValue("FieldDescriptors", FieldDescriptors);
+      info.AddValue(nameof(FieldTypes), typeNames);
+      info.AddValue(nameof(FieldDescriptors), FieldDescriptors);
     }
 
     /// <inheritdoc/>
     public override string ToString()
     {
       var sb = new ValueStringBuilder(stackalloc char[4096]);
-      for (int i = 0; i < FieldCount; i++) {
+      for (int i = 0, count = Count; i < count; i++) {
         if (i > 0)
           sb.Append(", ");
         sb.Append(FieldTypes[i].GetShortName());
@@ -177,7 +172,7 @@ public static TupleDescriptor Create(Type[] fieldTypes)
     {
       ArgumentValidator.EnsureArgumentNotNull(fieldTypes, nameof(fieldTypes));
       if (fieldTypes.Length == 0) {
-        return EmptyDescriptor;
+        return Empty;
       }
       return new TupleDescriptor(fieldTypes);
     }
@@ -285,12 +280,12 @@ private TupleDescriptor(Type[] fieldTypes)
 
     public TupleDescriptor(SerializationInfo info, StreamingContext context)
     {
-      ValuesLength = info.GetInt32("ValuesLength");
-      ObjectsLength = info.GetInt32("ObjectsLength");
+      ValuesLength = info.GetInt32(nameof(ValuesLength));
+      ObjectsLength = info.GetInt32(nameof(ObjectsLength));
 
-      var typeNames = (string[]) info.GetValue("FieldTypes", typeof(string[]));
+      var typeNames = (string[]) info.GetValue(nameof(FieldTypes), typeof(string[]));
       FieldDescriptors = (PackedFieldDescriptor[])info.GetValue(
-        "FieldDescriptors", typeof(PackedFieldDescriptor[]));
+        nameof(FieldDescriptors), typeof(PackedFieldDescriptor[]));
 
       FieldTypes = new Type[typeNames.Length];
       for (var i = 0; i < typeNames.Length; i++) {