Tighten prepared execution credential handling

backends.go

@@ -40,12 +40,12 @@ type Backend struct {
 	// calls allowed for this backend within one Engine. Zero leaves the backend
 	// unlimited. A negative value makes NewEngine fail with ErrInvalidConfig.
 	ConcurrencyLimit int
-	// QueueCapacity controls how many additional Run calls may be admitted
-	// beyond ConcurrencyLimit. Nil uses 1024 when ConcurrencyLimit is positive;
-	// a pointer uses its exact value, including zero. The pointed-to value must
-	// be non-negative, and QueueCapacity must be nil when ConcurrencyLimit is
-	// zero. Their sum must fit in an int. WithBackend copies the value and does
-	// not retain the pointer.
+	// QueueCapacity controls how many additional Run or RunPrepared calls may
+	// be admitted beyond ConcurrencyLimit. Nil uses 1024 when ConcurrencyLimit
+	// is positive; a pointer uses its exact value, including zero. The pointed-to
+	// value must be non-negative, and QueueCapacity must be nil when
+	// ConcurrencyLimit is zero. Their sum must fit in an int. WithBackend copies
+	// the value and does not retain the pointer.
 	QueueCapacity *int
 }