Avoid database lock timed backoff

1 files changed, 47 insertions, 32 deletions

diff --git a/main.go b/main.go
index 9601164..abb5994 100644
--- a/main.go
+++ b/main.go
@@ -2176,22 +2176,6 @@ func makeThumbnail(pathImage, pathThumb string) (int, int, error) {
 	return w, h, err
 }
 
-func makeThumbnailFor(sha1 string) (message string, err error) {
-	pathImage := imagePath(sha1)
-	pathThumb := thumbPath(sha1)
-	w, h, err := makeThumbnail(pathImage, pathThumb)
-	if err != nil {
-		if ee, ok := err.(*exec.ExitError); ok {
-			return string(ee.Stderr), nil
-		}
-		return "", err
-	}
-
-	_, err = db.Exec(`UPDATE image SET thumbw = ?, thumbh = ?
-		WHERE sha1 = ?`, w, h, sha1)
-	return "", err
-}
-
 // cmdThumbnail generates missing thumbnails, in parallel.
 func cmdThumbnail(fs *flag.FlagSet, args []string) error {
 	if err := fs.Parse(args); err != nil {
@@ -2214,7 +2198,31 @@ func cmdThumbnail(fs *flag.FlagSet, args []string) error {
 			return err
 		}
 	}
-	return parallelize(hexSHA1, makeThumbnailFor)
+
+	stmt, err := db.Prepare(
+		`UPDATE image SET thumbw = ?, thumbh = ? WHERE sha1 = ?`)
+	if err != nil {
+		return err
+	}
+	defer stmt.Close()
+
+	var mu sync.Mutex
+	return parallelize(hexSHA1, func(sha1 string) (message string, err error) {
+		pathImage := imagePath(sha1)
+		pathThumb := thumbPath(sha1)
+		w, h, err := makeThumbnail(pathImage, pathThumb)
+		if err != nil {
+			if ee, ok := err.(*exec.ExitError); ok {
+				return string(ee.Stderr), nil
+			}
+			return "", err
+		}
+
+		mu.Lock()
+		defer mu.Unlock()
+		_, err = stmt.Exec(w, h, sha1)
+		return "", err
+	})
 }
 
 // --- Perceptual hash ---------------------------------------------------------
@@ -2336,20 +2344,6 @@ func makeDhash(sha1 string) (uint64, error) {
 	return dhashWebP(f)
 }
 
-func makeDhashFor(sha1 string) (message string, err error) {
-	hash, err := makeDhash(sha1)
-	if errors.Is(err, errIsAnimation) {
-		// Ignoring this common condition.
-		return "", nil
-	} else if err != nil {
-		return err.Error(), nil
-	}
-
-	_, err = db.Exec(
-		`UPDATE image SET dhash = ? WHERE sha1 = ?`, int64(hash), sha1)
-	return "", err
-}
-
 // cmdDhash computes perceptual hashes from thumbnails.
 func cmdDhash(fs *flag.FlagSet, args []string) error {
 	if err := fs.Parse(args); err != nil {
@@ -2371,7 +2365,28 @@ func cmdDhash(fs *flag.FlagSet, args []string) error {
 			return err
 		}
 	}
-	return parallelize(hexSHA1, makeDhashFor)
+
+	stmt, err := db.Prepare(`UPDATE image SET dhash = ? WHERE sha1 = ?`)
+	if err != nil {
+		return err
+	}
+	defer stmt.Close()
+
+	var mu sync.Mutex
+	return parallelize(hexSHA1, func(sha1 string) (message string, err error) {
+		hash, err := makeDhash(sha1)
+		if errors.Is(err, errIsAnimation) {
+			// Ignoring this common condition.
+			return "", nil
+		} else if err != nil {
+			return err.Error(), nil
+		}
+
+		mu.Lock()
+		defer mu.Unlock()
+		_, err = stmt.Exec(int64(hash), sha1)
+		return "", err
+	})
 }
 
 // --- Main --------------------------------------------------------------------