I once wrote a stored procedure that did something that has now been built into most databases. I didn't write the original code, I just modified the code to us

I once wrote a stored procedure that did something that has now been built into most databases. I didn't write the original code, I just modified the code to use the information schema. It took me two days to understand the original code and two days to make my changes. For a few years after I wrote that code I got emails from random people asking me questions about it and I sadly could not help them.