From 84b89289a3bc95f1d27860b222ae2abc73cd5fa5 Mon Sep 17 00:00:00 2001
From: Lunny Xiao <xiaolunwen@gmail.com>
Date: Tue, 6 May 2014 11:11:44 +0800
Subject: [PATCH] start & limit implementation for mssql

---
 statement.go | 53 +++++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 40 insertions(+), 13 deletions(-)

diff --git a/statement.go b/statement.go
index 02078cb9..5185c91e 100644
--- a/statement.go
+++ b/statement.go
@@ -974,20 +974,52 @@ func (statement *Statement) genSelectSql(columnStr string) (a string) {
 		distinct = "DISTINCT "
 	}
 
-	// !nashtsai! REVIEW Sprintf is considered slowest mean of string concatnation, better to work with builder pattern
-	a = fmt.Sprintf("SELECT %v%v FROM %v", distinct, columnStr,
-		statement.Engine.Quote(statement.TableName()))
-	if statement.JoinStr != "" {
-		a = fmt.Sprintf("%v %v", a, statement.JoinStr)
+	var top string
+	var mssqlCondi string
+	var orderBy string
+	if statement.OrderStr != "" {
+		orderBy = fmt.Sprintf(" ORDER BY %v", statement.OrderStr)
 	}
 	statement.processIdParam()
+	var whereStr string
 	if statement.WhereStr != "" {
-		a = fmt.Sprintf("%v WHERE %v", a, statement.WhereStr)
+		whereStr = fmt.Sprintf(" WHERE %v", statement.WhereStr)
 		if statement.ConditionStr != "" {
-			a = fmt.Sprintf("%v AND %v", a, statement.ConditionStr)
+			whereStr = fmt.Sprintf("%v AND %v", whereStr, statement.ConditionStr)
 		}
 	} else if statement.ConditionStr != "" {
-		a = fmt.Sprintf("%v WHERE %v", a, statement.ConditionStr)
+		whereStr = fmt.Sprintf(" WHERE %v", statement.ConditionStr)
+	}
+	var fromStr string = " FROM " + statement.Engine.Quote(statement.TableName())
+	if statement.JoinStr != "" {
+		fromStr = fmt.Sprintf("%v %v", fromStr, statement.JoinStr)
+	}
+
+	if statement.Engine.dialect.DBType() == core.MSSQL {
+		top = fmt.Sprintf(" TOP %d", statement.LimitN)
+		if statement.Start > 0 {
+			var column string = "(id)"
+			if len(statement.RefTable.PKColumns()) == 0 {
+				for _, index := range statement.RefTable.Indexes {
+					if len(index.Cols) == 1 {
+						column = index.Cols[0]
+						break
+					}
+				}
+				if len(column) == 0 {
+					column = statement.RefTable.ColumnsSeq()[0]
+				}
+			}
+			mssqlCondi = fmt.Sprintf("(%s NOT IN (SELECT TOP %d %s%s%s%s))",
+				column, statement.Start, column, fromStr, whereStr, orderBy)
+		}
+	}
+
+	// !nashtsai! REVIEW Sprintf is considered slowest mean of string concatnation, better to work with builder pattern
+	a = fmt.Sprintf("SELECT %v%v%v%v%v", top, distinct, columnStr,
+		fromStr, whereStr)
+	if mssqlCondi != "" {
+		a += " AND " + mssqlCondi
 	}
 
 	if statement.GroupByStr != "" {
@@ -1005,11 +1037,6 @@ func (statement *Statement) genSelectSql(columnStr string) (a string) {
 		} else if statement.LimitN > 0 {
 			a = fmt.Sprintf("%v LIMIT %v", a, statement.LimitN)
 		}
-	} else {
-		//TODO: for mssql, should handler limit.
-		/*SELECT * FROM (
-		  SELECT *, ROW_NUMBER() OVER (ORDER BY id desc) as row FROM "userinfo"
-		 ) a WHERE row > [start] and row <= [start+limit] order by id desc*/
 	}
 
 	return