NH-3195 - Port-back.

Add support for variable limit with TOP (n) clause to MsSqlCeDialect

Author: hazzik

src/NHibernate/Dialect/MsSqlCe40Dialect.cs

@@ -4,11 +4,6 @@ namespace NHibernate.Dialect
 {
 	public class MsSqlCe40Dialect : MsSqlCeDialect
 	{
-		public override bool SupportsLimit
-		{
-			get { return true; }
-		}
-
 		public override bool SupportsLimitOffset
 		{
 			get { return true; }

src/NHibernate/Dialect/MsSqlCeDialect.cs

@@ -1,8 +1,10 @@
+using System;
 using System.Data;
 using System.Data.Common;
 using System.Text;
 using NHibernate.Dialect.Function;
 using NHibernate.Dialect.Schema;
+using NHibernate.SqlCommand;
 using NHibernate.Util;
 using Environment = NHibernate.Cfg.Environment;
 
@@ -111,7 +113,7 @@ public override string SelectGUIDString
 
 		public override bool SupportsLimit
 		{
-			get { return false; }
+			get { return true; }
 		}
 
 		public override bool SupportsLimitOffset
@@ -129,6 +131,17 @@ public override IDataBaseSchema GetDataBaseSchema(DbConnection connection)
 			return new MsSqlCeDataBaseSchema(connection);
 		}
 
+		public override SqlString GetLimitString(SqlString querySqlString, SqlString offset, SqlString limit)
+		{
+			var top = new SqlStringBuilder()
+				.Add(" top (")
+				.Add(limit)
+				.Add(")")
+				.ToSqlString();
+
+			return querySqlString.Insert(GetAfterSelectInsertPoint(querySqlString), top);
+		}
+
         public override string Qualify(string catalog, string schema, string table)
         {
             // SQL Server Compact doesn't support Schemas. So join schema name and table name with underscores
@@ -174,5 +187,18 @@ public override string Qualify(string catalog, string schema, string table)
                 name = OpenQuote + name + CloseQuote;
             return qualifiedName.Append(name).ToString();
         }
-    }
+
+		private static int GetAfterSelectInsertPoint(SqlString sql)
+		{
+			if (sql.StartsWithCaseInsensitive("select distinct"))
+			{
+				return 15;
+			}
+			if (sql.StartsWithCaseInsensitive("select"))
+			{
+				return 6;
+			}
+			throw new NotSupportedException("The query should start with 'SELECT' or 'SELECT DISTINCT'");
+		}
+	}
 }