MSSQL rows limit/offset via TOP or OFFSET ... FETCH NEXT ... ROWS

bdb/drivers/mock.go

@@ -118,6 +118,9 @@ func (m *MockDriver) PrimaryKeyInfo(schema, tableName string) (*bdb.PrimaryKey,
 // UseLastInsertID returns a database mock LastInsertID compatibility flag
 func (m *MockDriver) UseLastInsertID() bool { return false }
 
+// UseTopClause returns a database mock SQL TOP clause compatibility flag
+func (m *MockDriver) UseTopClause() bool { return false }
+
 // Open mimics a database open call and returns nil for no error
 func (m *MockDriver) Open() error { return nil }
 

bdb/drivers/mssql.go

@@ -64,8 +64,13 @@ func (m *MSSQLDriver) Close() {
 	m.dbConn.Close()
 }
 
-// UseLastInsertID returns false for postgres
+// UseLastInsertID returns false for mssql
 func (m *MSSQLDriver) UseLastInsertID() bool {
+	return false
+}
+
+// UseTopClause returns true to indicate MS SQL supports SQL TOP clause
+func (m *MSSQLDriver) UseTopClause() bool {
 	return true
 }
 

bdb/drivers/mysql.go

@@ -81,6 +81,11 @@ func (m *MySQLDriver) UseLastInsertID() bool {
 	return true
 }
 
+// UseTopClause returns false to indicate MySQL doesnt support SQL TOP clause
+func (m *MySQLDriver) UseTopClause() bool {
+	return false
+}
+
 // TableNames connects to the postgres database and
 // retrieves all table names from the information_schema where the
 // table schema is public.

bdb/drivers/postgres.go

@@ -78,6 +78,11 @@ func (p *PostgresDriver) UseLastInsertID() bool {
 	return false
 }
 
+// UseTopClause returns false to indicate PSQL doesnt support SQL TOP clause
+func (m *PostgresDriver) UseTopClause() bool {
+	return false
+}
+
 // TableNames connects to the postgres database and
 // retrieves all table names from the information_schema where the
 // table schema is schema. It uses a whitelist and blacklist.

bdb/interface.go

@@ -18,6 +18,10 @@ type Interface interface {
 	// the sql.Exec result's LastInsertId
 	UseLastInsertID() bool
 
+	// UseTopClause should return true if the Database is capable of using
+	// the SQL TOP clause
+	UseTopClause() bool
+
 	// Open the database connection
 	Open() error
 	// Close the database connection

bdb/interface_test.go

@@ -10,6 +10,7 @@ type testMockDriver struct{}
 
 func (m testMockDriver) TranslateColumnType(c Column) Column { return c }
 func (m testMockDriver) UseLastInsertID() bool               { return false }
+func (m testMockDriver) UseTopClause() bool                  { return false }
 func (m testMockDriver) Open() error                         { return nil }
 func (m testMockDriver) Close()                              {}
 

boilingcore/boilingcore.go

@@ -325,6 +325,7 @@ func (s *State) initDriver(driverName string) error {
 	s.Dialect.LQ = s.Driver.LeftQuote()
 	s.Dialect.RQ = s.Driver.RightQuote()
 	s.Dialect.IndexPlaceholders = s.Driver.IndexPlaceholders()
+	s.Dialect.UseTopClause = s.Driver.UseTopClause()
 
 	return nil
 }

queries/query.go

@@ -52,6 +52,9 @@ type Dialect struct {
 	// Bool flag indicating whether indexed
 	// placeholders ($1) are used, or ? placeholders.
 	IndexPlaceholders bool
+	// Bool flag indicating whether "TOP" or "LIMIT" clause
+	// must be used for rows limitation
+	UseTopClause bool
 }
 
 type where struct {

queries/query_builders.go

@@ -46,6 +46,12 @@ func buildSelectQuery(q *Query) (*bytes.Buffer, []interface{}) {
 
 	buf.WriteString("SELECT ")
 
+	if q.dialect.UseTopClause {
+		if q.limit != 0 && q.offset == 0 {
+			fmt.Fprintf(buf, " TOP (%d)", q.limit)
+		}
+	}
+
 	if q.count {
 		buf.WriteString("COUNT(")
 	}
@@ -308,11 +314,26 @@ func writeModifiers(q *Query, buf *bytes.Buffer, args *[]interface{}) {
 		buf.WriteString(strings.Join(q.orderBy, ", "))
 	}
 
-	if q.limit != 0 {
-		fmt.Fprintf(buf, " LIMIT %d", q.limit)
-	}
-	if q.offset != 0 {
-		fmt.Fprintf(buf, " OFFSET %d", q.offset)
+	if !q.dialect.UseTopClause {
+		if q.limit != 0 {
+			fmt.Fprintf(buf, " LIMIT %d", q.limit)
+		}
+
+		if q.offset != 0 {
+			fmt.Fprintf(buf, " OFFSET %d", q.offset)
+		}
+	} else {
+		// From MS SQL 2012 and above: https://technet.microsoft.com/en-us/library/ms188385(v=sql.110).aspx
+		// ORDER BY ...
+		// OFFSET N ROWS
+		// FETCH NEXT M ROWS ONLY
+		if q.offset != 0 {
+			fmt.Fprintf(buf, " OFFSET %d", q.offset)
+
+			if q.limit != 0 {
+				fmt.Fprintf(buf, " FETCH NEXT %d ROWS ONLY", q.limit)
+			}
+		}
 	}
 
 	if len(q.forlock) != 0 {