Yeah, these things are almost never as simple as they are supposed to be.
Poland has PESEL numbers since 70s. It was supposed to be unique, only apply to Polish citizens, never change, and have a checksum digit. Every Polish citizen gets one at 18 when they get their national ID document, and you can request it earlier if you want to.
Turns out there are duplicated PESEL numbers. A LOT of non-Polish citizens have them assigned (mostly Ukrainian refuges but not only). The checksums are sometimes wrong. And some people have several PESEL numbers.
If you used PESEL as database key you're fucked.
The system works perfectly, but it interfaces with external world through computer-human-paper-human-computer interface. And at some point the mistake propagates so far that it becomes the truth assumptions be damned.
Poland has PESEL numbers since 70s. It was supposed to be unique, only apply to Polish citizens, never change, and have a checksum digit. Every Polish citizen gets one at 18 when they get their national ID document, and you can request it earlier if you want to.
Turns out there are duplicated PESEL numbers. A LOT of non-Polish citizens have them assigned (mostly Ukrainian refuges but not only). The checksums are sometimes wrong. And some people have several PESEL numbers.
If you used PESEL as database key you're fucked.
The system works perfectly, but it interfaces with external world through computer-human-paper-human-computer interface. And at some point the mistake propagates so far that it becomes the truth assumptions be damned.