if optimistically assuming cksum unchanged, then do not get cksum, just update checked, modified

src/asses/db.go

@@ -56,6 +56,15 @@ func checked(ctx context.Context, p, cksum string, modified time.Time) error {
 		return err
 	}
 
+	if cksum != "" {
+	} else if err := db.Exec(ctx, `
+		UPDATE "asses.checks"
+		SET checked_at=$2, modified=$3
+		WHERE p=$1
+	`, p, time.Now(), modified); err == nil {
+		return nil
+	}
+
 	return db.Exec(ctx, `
 		INSERT INTO "asses.checks"
 		(p, checked_at, cksum, modified)

src/asses/one.go

@@ -48,9 +48,11 @@ func One(ctx context.Context, p string) error {
 		log.Printf("asses.One(%s) // modified (%v) is now %v", shortp, last.Modified, stat.ModTime())
    }
 
+   doCksum := true
 	if err := func() error {
 		if len(last.Cksum) > 0 {
          if last.Modified.IsZero() {
+            doCksum = false
 				log.Printf("asses.One(%s) // assume cksum unchanged given null modified ", shortp)
 				return nil
          }
@@ -76,10 +78,14 @@ func One(ctx context.Context, p string) error {
 		return err
 	}
 
-	cksum, err := Cksum(ctx, p)
+   var cksum string
-	if err != nil {
+   if doCksum {
-		return err
+      var err error
-	}
+	   cksum, err = Cksum(ctx, p)
+	   if err != nil {
+	   	return err
+	   }
+   }
 	stat, err := os.Stat(p)
 	if err != nil {
 		return err