Robert Haas talks about a development challenge:
Hacking on PostgreSQL is really hard. I think a lot of people would agree with this statement, not all for the same reasons. Some might point to the character of discourse on the mailing list, others to the shortage of patch reviewers, and others still to the difficulty of getting the attention of a committer, or of feeling like a hostage to some committer’s whimsy. All of these are problems, but today I want to focus on the purely technical aspect of the problem: the extreme difficulty of writing reasonably correct patches.
Read on for Robert’s experience developing incremental backups in Postgres. In fairness, I think this is true of any complex system which becomes mission-critical. It’s really easy to develop in low-risk, limited-code, greenfield environments. As you change each of those properties, development gets considerably more challenging, even if people are doing the right things the right way and checking ego at the door.