i haven't read the source code for bitcoind, but i want to know if it downloads bad blocks which will later be rejected by the network (and presumably later removed from bitcoind's block files)?

i have a script which parses block files into a database and if a block is in the files at one point in time, then gets removed later then my script (as it currently stands) will end up importing the incorrect block.

if bitcoind does download bad blocks, how should i avoid importing these into my database? should i just wait and never import the latest, say, 5 blocks?