Performance for the DefaultUidGenerator

It is time-consuming for currentTimeMillis ===> seconds
long currentSecond = TimeUnit.MILLISECONDS.toSeconds(System.currentTimeMillis());
under method getCurrentSecond().

After i change to currentTimeMillis instead of transferring to seconds,
It is much faster. Otherwise DefaultUidGenerator is very slow.

Start by locating getCurrentSecond() and reading the callers that depend on its returned time value. Compare the current conversion with the proposed currentTimeMillis change, then verify that the generator's timestamp behavior remains correct while measuring whether the reported performance problem is resolved.

Written by the indexing model from the issue text.