madlib/madlib — pull request #250 by KevinYL (2012-10-15 01:27:19+00:00)
Title: Madlib 689

In order to fix the security issues of the sketch method described in MADLIB-630, at the entry point of each UDF, we did strictly checking of the contents stored in a vararea to make sure that each access to elements in the vararea is safe. This checking degenerates the performance.

Because these step functions only access each item at most one time on each call, in order to avoid performance degeneration, we only do checking when access the specific element. The performance
degeneration decreases from 50% at most to 20%.