Megatest

  (let* ((backupfname (conc fname"-"(current-process-id)".bak"))
	 (cmd (conc "cp "fname" "backupfname";mv "fname" "(conc fname ".delme;")
		    "cp "backupfname" "fname)))
    (dbfile:print-err "WARNING: attempting recovery of file "fname" by running commands:\n"
		      "  "cmd)
    (system cmd)))


(define (dbfile:open-no-sync-db dbpath)
  (if *no-sync-db*
      *no-sync-db*
      (begin
	(if (not (file-exists? dbpath))
	    (create-directory dbpath #t))
	(let* ((dbname    (conc dbpath "/no-sync.db"))
	       (db-exists (file-exists? dbname))
	       (init-proc (lambda (db)
			    (if (not db-exists)
				(begin
				  (sqlite3:execute db "CREATE TABLE IF NOT EXISTS no_sync_metadat (var TEXT,val TEXT, CONSTRAINT no_sync_metadat_constraint UNIQUE (var));"))
				)))
	       (on-tmp      (equal? (car (string-split dbpath "/")) "tmp"))
	       (db        (if on-tmp
			      (dbfile:cautious-open-database dbname init-proc 0 "WAL")
			      (sqlite3:open-database dbname))))
	  (if on-tmp	      ;; done in cautious-open-database
	      (begin
		(sqlite3:execute db "PRAGMA synchronous = 0;")
		(sqlite3:set-busy-handler! db (sqlite3:make-busy-timeout 136000))))
	  (set! *no-sync-db* db)
	  db))))

(define (db:no-sync-set db var val)
  (sqlite3:execute db "INSERT OR REPLACE INTO no_sync_metadat (var,val) VALUES (?,?);" var val))

(define (db:no-sync-del! db var)