Strip redundant Cast operations

Author: AlexUstinov

Orm/Xtensive.Orm/Orm/Providers/SqlCompiler.Apply.cs

@@ -92,10 +92,11 @@ private SqlSelect ProcessApplyViaSubqueries(ApplyProvider provider, SqlProvider
       if (shouldUseQueryReference) {
         var leftTable = left.PermanentReference;
         query = SqlDml.Select(leftTable);
-        query.Columns.AddRange(leftTable.Columns.Cast<SqlColumn>());
+        query.Columns.AddRange(leftTable.Columns);
       }
-      else
+      else {
         query = left.Request.Statement.ShallowClone();
+      }
 
       var isApplyExistence =
         provider.Right.Type==ProviderType.Existence ||

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

@@ -81,7 +81,7 @@ protected static SqlSelect ExtractSqlSelect(CompilableProvider origin, SqlProvid
       if (ShouldUseQueryReference(origin, compiledSource)) {
         var queryRef = compiledSource.PermanentReference;
         var query = SqlDml.Select(queryRef);
-        query.Columns.AddRange(queryRef.Columns.Cast<SqlColumn>());
+        query.Columns.AddRange(queryRef.Columns);
         return query;
       }
       return sourceSelect.ShallowClone();

Orm/Xtensive.Orm/Orm/Providers/SqlCompiler.Index.cs

@@ -94,7 +94,7 @@ private SqlSelect BuildUnionQuery(IndexInfo index)
 
       var unionRef = SqlDml.QueryRef(result);
       var query = SqlDml.Select(unionRef);
-      query.Columns.AddRange(unionRef.Columns.Cast<SqlColumn>());
+      query.Columns.AddRange(unionRef.Columns);
       return query;
     }
 

Orm/Xtensive.Orm/Orm/Providers/SqlCompiler.Paging.cs

@@ -88,7 +88,7 @@ private SqlProvider VisitSkipRowNumber(SkipProvider provider)
       var source = compiledSource.Request.Statement;
       var queryRef = SqlDml.QueryRef(source);
       var query = SqlDml.Select(queryRef);
-      query.Columns.AddRange(queryRef.Columns.Cast<SqlColumn>());
+      query.Columns.AddRange(queryRef.Columns);
       query.Where = queryRef.Columns.Last() > skipParameterBinding.ParameterReference;
       return CreateProvider(query, bindings, provider, compiledSource);
     }
@@ -101,7 +101,7 @@ private SqlProvider VisitTakeRowNumber(TakeProvider provider)
       var source = compiledSource.Request.Statement;
       var queryRef = SqlDml.QueryRef(source);
       var query = SqlDml.Select(queryRef);
-      query.Columns.AddRange(queryRef.Columns.Cast<SqlColumn>());
+      query.Columns.AddRange(queryRef.Columns);
       query.Where = queryRef.Columns.Last() <= takeParameterBinding.ParameterReference;
       return CreateProvider(query, bindings, provider, compiledSource);
     }
@@ -116,7 +116,7 @@ private SqlProvider VisitPagingRowNumber(PagingProvider provider)
       var queryRef = SqlDml.QueryRef(source);
       var query = SqlDml.Select(queryRef);
       var rowNumberColumn = queryRef.Columns.Last();
-      query.Columns.AddRange(queryRef.Columns.Cast<SqlColumn>());
+      query.Columns.AddRange(queryRef.Columns);
       query.Where = SqlDml.Between(rowNumberColumn,
         fromParameterBinding.ParameterReference,
         toParameterBinding.ParameterReference);