NH-2977

- Added limit SQL generation for SQL Server queries with comments, common table expressions, and stored procedure invocations.
- Modified loader to fall back to client-side limit/offset behavior if dialect does not support generation of server side limit/offset SQL for a given (custom) SQL statement.

Author: ggeurts

src/NHibernate.Test/DialectTest/MsSql2005DialectFixture.cs

@@ -75,7 +75,7 @@ public void OnlyOffsetLimit()
 			var d = new MsSql2005Dialect();
 
 			SqlString str = d.GetLimitString(new SqlString("select distinct c.Contact_Id as Contact1_19_0_, c._Rating as Rating2_19_0_ from dbo.Contact c where COALESCE(c.Rating, 0) > 0 order by c.Rating desc , c.Last_Name , c.First_Name"), null, new SqlString("10"));
-			Assert.That(str.ToString(), Is.EqualTo("select distinct TOP (10)  c.Contact_Id as Contact1_19_0_, c._Rating as Rating2_19_0_ from dbo.Contact c where COALESCE(c.Rating, 0) > 0 order by c.Rating desc , c.Last_Name , c.First_Name"));
+			Assert.That(str.ToString(), Is.EqualTo("select distinct TOP (10) c.Contact_Id as Contact1_19_0_, c._Rating as Rating2_19_0_ from dbo.Contact c where COALESCE(c.Rating, 0) > 0 order by c.Rating desc , c.Last_Name , c.First_Name"));
 		}
 
 		[Test]
@@ -222,7 +222,85 @@ public void GetIfExistsDropConstraintTest_For_Schema_other_than_dbo()
 		public void GetLimitStringWithSqlComments()
 		{
 			var d = new MsSql2005Dialect();
-			Assert.Throws<NotSupportedException>(() => d.GetLimitString(new SqlString(" /* criteria query */ SELECT p from lcdtm"), null, new SqlString("2")));
+			var limitSqlQuery = d.GetLimitString(new SqlString(" /* criteria query */ SELECT p from lcdtm"), null, new SqlString("2"));
+			Assert.That(limitSqlQuery, Is.Not.Null);
+			Assert.That(limitSqlQuery.ToString(), Is.EqualTo(" /* criteria query */ SELECT TOP (2) p from lcdtm"));
+		}
+
+		[Test]
+		public void GetLimitStringWithSqlCommonTableExpression()
+		{
+			const string SQL = @"
+				WITH DirectReports (ManagerID, EmployeeID, Title, DeptID, Level)
+				(   -- Anchor member definition
+					SELECT  ManagerID, EmployeeID, Title, Deptid, 0 AS Level
+					FROM    MyEmployees
+					WHERE   ManagerID IS NULL
+					
+					UNION ALL
+					
+					-- Recursive member definition
+					SELECT  e.ManagerID, e.EmployeeID, e.Title, e.Deptid, Level + 1
+					FROM    MyEmployees AS e
+					INNER JOIN DirectReports AS ON e.ManagerID = d.EmployeeID
+				)
+				-- Statement that executes the CTE
+				SELECT  ManagerID, EmployeeID, Title, Level
+				FROM    DirectReports";
+
+			const string EXPECTED_SQL = @"
+				WITH DirectReports (ManagerID, EmployeeID, Title, DeptID, Level)
+				(   -- Anchor member definition
+					SELECT  ManagerID, EmployeeID, Title, Deptid, 0 AS Level
+					FROM    MyEmployees
+					WHERE   ManagerID IS NULL
+					
+					UNION ALL
+					
+					-- Recursive member definition
+					SELECT  e.ManagerID, e.EmployeeID, e.Title, e.Deptid, Level + 1
+					FROM    MyEmployees AS e
+					INNER JOIN DirectReports AS ON e.ManagerID = d.EmployeeID
+				)
+				-- Statement that executes the CTE
+				SELECT  TOP (2) ManagerID, EmployeeID, Title, Level
+				FROM    DirectReports";
+
+			var d = new MsSql2005Dialect();
+			var limitSqlQuery = d.GetLimitString(new SqlString(SQL), null, new SqlString("2"));
+			Assert.That(limitSqlQuery, Is.Not.Null);
+			Assert.That(limitSqlQuery.ToString(), Is.EqualTo(EXPECTED_SQL));
+		}
+
+		[Test]
+		public void DontReturnLimitStringForStoredProcedureCall()
+		{
+			VerifyLimitStringForStoredProcedureCalls("EXEC sp_stored_procedures");
+			VerifyLimitStringForStoredProcedureCalls(@"
+				DECLARE @id int
+				SELECT  @id = id FROM persons WHERE name LIKE ?
+				EXEC    get_person_summary @id");
+			VerifyLimitStringForStoredProcedureCalls(@"
+				DECLARE @id int
+				SELECT DISTINCT TOP 1 @id = id FROM persons WHERE name LIKE ?
+				EXEC    get_person_summary @id");
+			VerifyLimitStringForStoredProcedureCalls(@"
+				DECLARE @id int
+				SELECT DISTINCT TOP (?) PERCENT WITH TIES @id = id FROM persons WHERE name LIKE ?
+				EXEC    get_person_summary @id");
+		}
+
+		private static void VerifyLimitStringForStoredProcedureCalls(string sql)
+		{
+			var d = new MsSql2005Dialect();
+			var limitSql = d.GetLimitString(new SqlString(sql), null, new SqlString("2"));
+			Assert.That(limitSql, Is.Null, "Limit only: {0}", sql);
+
+			limitSql = d.GetLimitString(new SqlString(sql), new SqlString("10"), null);
+			Assert.That(limitSql, Is.Null, "Offset only: {0}", sql);
+
+			limitSql = d.GetLimitString(new SqlString(sql), new SqlString("10"), new SqlString("2"));
+			Assert.That(limitSql, Is.Null, "Limit and Offset: {0}", sql);
 		}
 	}
 }

src/NHibernate.Test/NHSpecificTest/NH2977/FixtureByCode.cs

@@ -0,0 +1,52 @@
+using NHibernate.Cfg.MappingSchema;
+using NUnit.Framework;
+
+namespace NHibernate.Test.NHSpecificTest.NH2977
+{
+	/// <summary>
+	/// Fixture using 'by code' mappings
+	/// </summary>
+	/// <remarks>
+	/// This fixture is identical to <see cref="Fixture" /> except the <see cref="Entity" /> mapping is performed 
+	/// by code in the GetMappings method, and does not require the <c>Mappings.hbm.xml</c> file. Use this approach
+	/// if you prefer.
+	/// </remarks>
+	public class ByCodeFixture : TestCaseMappingByCode
+	{
+		protected override HbmMapping GetMappings()
+		{
+			return new HbmMapping();
+		}
+
+		protected override bool AppliesTo(Dialect.Dialect dialect)
+		{
+			return dialect is Dialect.MsSql2000Dialect;
+		}
+
+		[Test]
+		public void CanGetUniqueStoredProcedureResult()
+		{
+			using (ISession session = OpenSession())
+			using (session.BeginTransaction())
+			{
+				var result = session.CreateSQLQuery("EXEC sp_stored_procedures ?")
+					.SetString(0, "sp_help")
+					.UniqueResult();
+				Assert.That(result, Is.Not.Null);
+			}
+		}
+
+		[Test]
+		public void CanLimitStoredProcedureResults()
+		{
+			using (ISession session = OpenSession())
+			using (session.BeginTransaction())
+			{
+				var result = session.CreateSQLQuery("EXEC sp_stored_procedures")
+					.SetMaxResults(5)
+					.List();
+				Assert.That(result, Has.Count.EqualTo(5));
+			}
+		}
+	}
+}

src/NHibernate.Test/NHibernate.Test.csproj

@@ -1036,6 +1036,7 @@
     <Compile Include="NHSpecificTest\NH2960\Fixture.cs" />
     <Compile Include="NHSpecificTest\NH2959\Entity.cs" />
     <Compile Include="NHSpecificTest\NH2959\Fixture.cs" />
+    <Compile Include="NHSpecificTest\NH2977\FixtureByCode.cs" />
     <Compile Include="NHSpecificTest\NH3010\FixtureWithBatcher.cs" />
     <Compile Include="NHSpecificTest\NH3010\FixtureWithNoBatcher.cs" />
     <Compile Include="NHSpecificTest\NH3010\Model.cs" />

src/NHibernate/Dialect/Dialect.cs

@@ -1452,20 +1452,22 @@ public virtual bool OffsetStartsAtOne
 		}
 
 		/// <summary>
-		/// Add a <c>LIMIT</c> clause to the given SQL <c>SELECT</c>.
+		/// Attempts to add a <c>LIMIT</c> clause to the given SQL <c>SELECT</c>.
 		/// Expects any database-specific offset and limit adjustments to have already been performed (ex. UseMaxForLimit, OffsetStartsAtOne).
 		/// </summary>
 		/// <param name="queryString">The <see cref="SqlString"/> to base the limit query off.</param>
 		/// <param name="offset">Offset of the first row to be returned by the query.  This may be represented as a parameter, a string literal, or a null value if no limit is requested.  This should have already been adjusted to account for OffsetStartsAtOne.</param>
 		/// <param name="limit">Maximum number of rows to be returned by the query.  This may be represented as a parameter, a string literal, or a null value if no offset is requested.  This should have already been adjusted to account for UseMaxForLimit.</param>
-		/// <returns>A new <see cref="SqlString"/> that contains the <c>LIMIT</c> clause.</returns>
+		/// <returns>A new <see cref="SqlString"/> that contains the <c>LIMIT</c> clause. Returns <c>null</c> 
+		/// if <paramref name="queryString"/> represents a SQL statement to which a limit clause cannot be added, 
+		/// for example when the query string is custom SQL invoking a stored procedure.</returns>
 		public virtual SqlString GetLimitString(SqlString queryString, SqlString offset, SqlString limit)
 		{
 			throw new NotSupportedException("Dialect does not have support for limit strings.");
 		}
 
 		/// <summary>
-		/// Generates a string to limit the result set to a number of maximum results with a specified offset into the results.
+		/// Attempts to generate a string to limit the result set to a number of maximum results with a specified offset into the results.
 		/// Expects any database-specific offset and limit adjustments to have already been performed (ex. UseMaxForLimit, OffsetStartsAtOne).
 		/// Performs error checking based on the various dialect limit support options.  If both parameters and fixed valeus are
 		/// specified, this will use the parameter option if possible.  Otherwise, it will fall back to a fixed string.

src/NHibernate/Dialect/MsSql2000Dialect.cs

@@ -9,6 +9,7 @@
 using NHibernate.Engine;
 using NHibernate.Mapping;
 using NHibernate.SqlCommand;
+using NHibernate.SqlCommand.Parser;
 using NHibernate.Type;
 using NHibernate.Util;
 using Environment = NHibernate.Cfg.Environment;
@@ -340,15 +341,26 @@ public override bool SupportsVariableLimit
 
 		public override SqlString GetLimitString(SqlString querySqlString, SqlString offset, SqlString limit)
 		{
-			/*
-			 * "SELECT TOP limit rest-of-sql-statement"
-			 */
+			int insertPoint;
+			return TryFindLimitInsertPoint(querySqlString, out insertPoint)
+				? querySqlString.Insert(insertPoint, new SqlString("top ", limit, " "))
+				: null;
+		}
 
-			SqlStringBuilder topFragment = new SqlStringBuilder();
-			topFragment.Add(" top ");
-			topFragment.Add(limit);
+		protected static bool TryFindLimitInsertPoint(SqlString sql, out int result)
+		{
+			var tokenEnum = new SqlTokenizer(sql).GetEnumerator();
+			
+			SqlToken selectToken;
+			bool isDistinct;
+			if (tokenEnum.TryParseUntilFirstMsSqlSelectColumn(out selectToken, out isDistinct))
+			{
+				result = tokenEnum.Current.SqlIndex;
+				return true;
+			}
 
-			return querySqlString.Insert(GetAfterSelectInsertPoint(querySqlString), topFragment.ToSqlString());
+			result = -1;
+			return false;
 		}
 
 		/// <summary>
@@ -398,19 +410,6 @@ public override string UnQuote(string quoted)
 			return quoted.Replace(new string(CloseQuote, 2), CloseQuote.ToString());
 		}
 
-		private static int GetAfterSelectInsertPoint(SqlString sql)
-		{
-			if (sql.StartsWithCaseInsensitive("select distinct"))
-			{
-				return 15;
-			}
-			else if (sql.StartsWithCaseInsensitive("select"))
-			{
-				return 6;
-			}
-			throw new NotSupportedException("The query should start with 'SELECT' or 'SELECT DISTINCT'");
-		}
-
 		protected bool NeedsLockHint(LockMode lockMode)
 		{
 			return lockMode.GreaterThan(LockMode.Read);

src/NHibernate/Dialect/MsSql2005Dialect.cs

@@ -103,4 +103,4 @@ public override string AppendLockHint(LockMode lockMode, string tableName)
 			return tableName;
 		}
 	}
-}
+}