Revert "Merge pull request #54 from ChenHuajun/discardall"

This reverts commit eb2835bd13aea7ca8bf7d0357d72491c9e5084cf, reversing
changes made to 5e645045b0a5f48e6f8303f7760d59dd76b1ae1e.

There was a problem with pull request #54 and postgresql below 9.0 regarding extra_float_digits