Merge pull request #231 from zhangyongding/chore-oralce-select-offset-fetch

change the Oracle select to use OFFSET...FETCH

Author: huandu

select.go

@@ -6,7 +6,6 @@ package sqlbuilder
 import (
 	"fmt"
 	"reflect"
-	"strings"
 
 	"github.com/huandu/go-clone"
 )
@@ -374,8 +373,6 @@ func (sb *SelectBuilder) BuildWithFlavor(flavor Flavor, initialArg ...interface{
 	buf := newStringBuilder()
 	sb.injection.WriteTo(buf, selectMarkerInit)
 
-	oraclePage := flavor == Oracle && (len(sb.limitVar) > 0 || len(sb.offsetVar) > 0)
-
 	if sb.cteBuilderVar != "" {
 		buf.WriteLeadingString(sb.cteBuilderVar)
 		sb.injection.WriteTo(buf, selectMarkerAfterWith)
@@ -388,51 +385,11 @@ func (sb *SelectBuilder) BuildWithFlavor(flavor Flavor, initialArg ...interface{
 			buf.WriteString("DISTINCT ")
 		}
 
-		if oraclePage {
-			var selectCols = make([]string, 0, len(sb.selectCols))
-			for i := range sb.selectCols {
-				cols := strings.SplitN(sb.selectCols[i], ".", 2)
-
-				if len(cols) == 1 {
-					selectCols = append(selectCols, cols[0])
-				} else {
-					selectCols = append(selectCols, cols[1])
-				}
-			}
-			buf.WriteStrings(selectCols, ", ")
-		} else {
-			buf.WriteStrings(sb.selectCols, ", ")
-		}
+		buf.WriteStrings(sb.selectCols, ", ")
 	}
 
 	sb.injection.WriteTo(buf, selectMarkerAfterSelect)
 
-	if oraclePage {
-		if len(sb.selectCols) > 0 {
-			buf.WriteLeadingString("FROM (SELECT ")
-
-			if sb.distinct {
-				buf.WriteString("DISTINCT ")
-			}
-
-			var selectCols = make([]string, 0, len(sb.selectCols)+1)
-			selectCols = append(selectCols, "ROWNUM r")
-
-			for i := range sb.selectCols {
-				cols := strings.SplitN(sb.selectCols[i], ".", 2)
-				if len(cols) == 1 {
-					selectCols = append(selectCols, cols[0])
-				} else {
-					selectCols = append(selectCols, cols[1])
-				}
-			}
-
-			buf.WriteStrings(selectCols, ", ")
-			buf.WriteLeadingString("FROM (SELECT ")
-			buf.WriteStrings(sb.selectCols, ", ")
-		}
-	}
-
 	tableNames := sb.TableNames()
 
 	if len(tableNames) > 0 {
@@ -562,34 +519,20 @@ func (sb *SelectBuilder) BuildWithFlavor(flavor Flavor, initialArg ...interface{
 		}
 
 	case Oracle:
-		if oraclePage {
-			buf.WriteString(") ")
+		if len(sb.offsetVar) > 0 {
+			buf.WriteLeadingString("OFFSET ")
+			buf.WriteString(sb.offsetVar)
+			buf.WriteString(" ROWS")
+		}
 
-			if len(sb.tables) > 0 {
-				buf.WriteStrings(sb.tables, ", ")
+		if len(sb.limitVar) > 0 {
+			if len(sb.offsetVar) == 0 {
+				buf.WriteLeadingString("OFFSET 0 ROWS")
 			}
 
-			buf.WriteString(") WHERE ")
-
-			if len(sb.limitVar) > 0 {
-				buf.WriteString("r BETWEEN ")
-
-				if len(sb.offsetVar) > 0 {
-					buf.WriteString(sb.offsetVar)
-					buf.WriteString(" + 1 AND ")
-					buf.WriteString(sb.limitVar)
-					buf.WriteString(" + ")
-					buf.WriteString(sb.offsetVar)
-				} else {
-					buf.WriteString("1 AND ")
-					buf.WriteString(sb.limitVar)
-				}
-			} else {
-				// As oraclePage is true, sb.offsetVar must not be empty.
-				buf.WriteString("r >= ")
-				buf.WriteString(sb.offsetVar)
-				buf.WriteString(" + 1")
-			}
+			buf.WriteLeadingString("FETCH NEXT ")
+			buf.WriteString(sb.limitVar)
+			buf.WriteString(" ROWS ONLY")
 		}
 
 	case Informix:

select_test.go

@@ -261,10 +261,10 @@ func ExampleSelectBuilder_limit_offset() {
 	//
 	// Oracle
 	// #1: SELECT * FROM user
-	// #2: SELECT * FROM (SELECT ROWNUM r, * FROM (SELECT * FROM user) user) WHERE r >= :1 + 1
-	// #3: SELECT * FROM (SELECT ROWNUM r, * FROM (SELECT * FROM user) user) WHERE r BETWEEN :1 + 1 AND :2 + :3
-	// #4: SELECT * FROM (SELECT ROWNUM r, * FROM (SELECT * FROM user) user) WHERE r BETWEEN 1 AND :1
-	// #5: SELECT * FROM (SELECT ROWNUM r, * FROM (SELECT * FROM user ORDER BY id) user) WHERE r BETWEEN :1 + 1 AND :2 + :3
+	// #2: SELECT * FROM user OFFSET :1 ROWS
+	// #3: SELECT * FROM user OFFSET :1 ROWS FETCH NEXT :2 ROWS ONLY
+	// #4: SELECT * FROM user OFFSET 0 ROWS FETCH NEXT :1 ROWS ONLY
+	// #5: SELECT * FROM user ORDER BY id OFFSET :1 ROWS FETCH NEXT :2 ROWS ONLY
 	//
 	// Informix
 	// #1: SELECT * FROM user