def raw_timestamp_to_cache_version(timestamp)
        key = timestamp.delete("- :.")
        if key.length < 20
          key.ljust(20, "0")
        else
          key
        end
      end
def raw_timestamp_to_cache_version(timestamp)
        key = timestamp.delete("- :.")
        if key.length < 20
          key.ljust(20, "0")
        else
          key
        end
      end
Converts a raw database string to `:usec`
 format.

 Example:

   timestamp = "2018-10-15 20:02:15.266505"
   raw_timestamp_to_cache_version(timestamp)
   # => "20181015200215266505"

 PostgreSQL truncates trailing zeros,
 https://github.com/postgres/postgres/commit/3e1beda2cde3495f41290e1ece5d544525810214
 to account for this we pad the output with zeros