Fix short path

database.go

@@ -20,7 +20,7 @@ type database struct {
 	// Other things
 	pc    singleflight.Group // persistant cache
 	pcm   sync.Mutex         // post creation
-	sp    singleflight.Group // singleflight group for short path requests
+	sp    sync.Mutex         // short path creation
 	debug bool
 }
 

postsFuncs.go

@@ -19,8 +19,8 @@ func (a *goBlog) fullPostURL(p *post) string {
 
 func (a *goBlog) shortPostURL(p *post) string {
 	s, err := a.db.shortenPath(p.Path)
-	if err != nil {
-		return p.Path
+	if err != nil || s == "" {
+		return a.getFullAddress(p.Path)
 	}
 	if a.cfg.Server.ShortPublicAddress != "" {
 		return a.cfg.Server.ShortPublicAddress + s

shortPath.go

@@ -11,16 +11,15 @@ func (db *database) shortenPath(p string) (string, error) {
 		return "", errors.New("empty path")
 	}
 
-	// Use singleflight to deduplicate concurrent requests and handle caching
-	v, err, _ := db.sp.Do(p, func() (interface{}, error) {
-		return db.shortenPathTransaction(p)
-	})
+	db.sp.Lock()
+	defer db.sp.Unlock()
 
+	result, err := db.shortenPathTransaction(p)
 	if err != nil {
 		return "", err
 	}
 
-	return v.(string), nil
+	return result, nil
 }
 
 func (db *database) shortenPathTransaction(p string) (string, error) {
@@ -33,14 +32,24 @@ func (db *database) shortenPathTransaction(p string) (string, error) {
 	var id int64
 	err = tx.QueryRow("select id from shortpath where path = @path", sql.Named("path", p)).Scan(&id)
 	if err == sql.ErrNoRows {
-		// Path doesn't exist, insert new entry
+		// Path doesn't exist, insert new entry with the lowest available id
 		result, err := tx.Exec(`
-            insert into shortpath (id, path)
-			values (
-				(select min(id) + 1 from (select id from shortpath union all select 0) where id + 1 not in (select id from shortpath)),
-				@path
-			)
-        `, sql.Named("path", p))
+            INSERT INTO shortpath (id, path)
+            VALUES (
+                (WITH RECURSIVE ids(n) AS (
+                    SELECT 1
+                    UNION ALL
+                    SELECT n + 1 FROM ids
+                    WHERE n < (SELECT COALESCE(MAX(id), 0) + 1 FROM shortpath)
+                )
+                SELECT n FROM ids
+                LEFT JOIN shortpath s ON ids.n = s.id
+                WHERE s.id IS NULL
+                ORDER BY n
+                LIMIT 1),
+                ?
+            )
+        `, p)
 		if err != nil {
 			return "", err
 		}

shortPath_test.go

@@ -17,28 +17,35 @@ func Test_shortenPath(t *testing.T) {
 
 	res1, err := db.shortenPath("/a")
 	require.NoError(t, err)
+	assert.Equal(t, "/s/1", res1)
 
 	res2, err := db.shortenPath("/a")
 	require.NoError(t, err)
+	assert.Equal(t, "/s/1", res2)
 
 	res3, err := db.shortenPath("/b")
 	require.NoError(t, err)
+	assert.Equal(t, "/s/2", res3)
 
 	res4, err := db.shortenPath("/a")
 	require.NoError(t, err)
+	assert.Equal(t, "/s/1", res4)
 
-	assert.Equal(t, res1, res2)
-	assert.Equal(t, "/s/1", res1)
+	res5, err := db.shortenPath("/c")
+	require.NoError(t, err)
+	assert.Equal(t, "/s/3", res5)
 
-	assert.NotEqual(t, res1, res3)
-	assert.Equal(t, "/s/2", res3)
+	_, err = db.Exec("delete from shortpath where id = 2")
+	require.NoError(t, err)
 
-	assert.Equal(t, res2, res4)
-	assert.Equal(t, "/s/1", res4)
+	res6, err := db.shortenPath("/d")
+	require.NoError(t, err)
+	assert.Equal(t, "/s/2", res6)
 
-	_, _ = db.Exec("delete from shortpath where id = 1")
+	_, err = db.Exec("delete from shortpath where id = 1")
+	require.NoError(t, err)
 
-	res5, err := db.shortenPath("/c")
+	res7, err := db.shortenPath("/e")
 	require.NoError(t, err)
-	assert.Equal(t, "/s/1", res5)
+	assert.Equal(t, "/s/1", res7)
 }