Merge pull request #361 from vkd/v4

fix iterator across empty pages

iterator.go

@@ -46,25 +46,32 @@ func (it *ScanIterator) Next() bool {
 		return true
 	}
 
-	// Return if there is more data to fetch.
-	if it.ScanCmd.cursor == 0 {
-		return false
-	}
+	for {
+		// Return if there is no more data to fetch.
+		if it.ScanCmd.cursor == 0 {
+			return false
+		}
 
-	// Fetch next page.
-	if it.ScanCmd._args[0] == "scan" {
-		it.ScanCmd._args[1] = it.ScanCmd.cursor
-	} else {
-		it.ScanCmd._args[2] = it.ScanCmd.cursor
-	}
-	it.ScanCmd.reset()
-	it.client.process(it.ScanCmd)
-	if it.ScanCmd.Err() != nil {
-		return false
-	}
+		// Fetch next page.
+		if it.ScanCmd._args[0] == "scan" {
+			it.ScanCmd._args[1] = it.ScanCmd.cursor
+		} else {
+			it.ScanCmd._args[2] = it.ScanCmd.cursor
+		}
+		it.ScanCmd.reset()
+		it.client.process(it.ScanCmd)
+		if it.ScanCmd.Err() != nil {
+			return false
+		}
 
-	it.pos = 1
-	return len(it.ScanCmd.page) > 0
+		it.pos = 1
+
+		// Redis can occasionally return empty page
+		if len(it.ScanCmd.page) > 0 {
+			return true
+		}
+	}
+	return false
 }
 
 // Val returns the key/field at the current cursor position.

iterator_test.go

@@ -21,6 +21,18 @@ var _ = Describe("ScanIterator", func() {
 		return err
 	}
 
+	var extraSeed = func(n int, m int) error {
+		pipe := client.Pipeline()
+		for i := 1; i <= m; i++ {
+			pipe.Set(fmt.Sprintf("A%02d", i), "x", 0).Err()
+		}
+		for i := 1; i <= n; i++ {
+			pipe.Set(fmt.Sprintf("K%02d", i), "x", 0).Err()
+		}
+		_, err := pipe.Exec()
+		return err
+	}
+
 	var hashKey = "K_HASHTEST"
 	var hashSeed = func(n int) error {
 		pipe := client.Pipeline()
@@ -110,4 +122,15 @@ var _ = Describe("ScanIterator", func() {
 		Expect(vals).To(HaveLen(13))
 	})
 
+	It("should scan with match across empty pages", func() {
+		Expect(extraSeed(2, 10)).NotTo(HaveOccurred())
+
+		var vals []string
+		iter := client.Scan(0, "K*", 1).Iterator()
+		for iter.Next() {
+			vals = append(vals, iter.Val())
+		}
+		Expect(iter.Err()).NotTo(HaveOccurred())
+		Expect(vals).To(HaveLen(2))
+	})
 })