Why tchdb file size keep going bigger after tchdbout some items?

I use tchdb in a server to store some data. And use another program to clean some old and useless data. But after executing this cleaner the file size didn't change and keep going bigger while the server still running. Did I do things wrong? Should I do something else in the server after executing the开发者_Python百科 cleaner?

Open mode for tchdbopen is HDBOREADER | HDBOWRITER | HDBOCREAT | HDBONOLCK.