It may be even easier. AFAIR, it's possible just to tell OS expected allocation without doing it. This way nothing changes for general code, it's only needed to specify expected file size on creation.
On 2015-05-21 11:54:40 -0700, Josh Berkus wrote: > This has been talked about as a feature, but would require major work on > PostgreSQL to make it possible. You'd be looking at several months of > effort by a really good hacker, and then a whole bunch of performance > testing. If you have the budget for this, then please let's talk about > it because right now nobody is working on it.
I think this is overestimating the required effort quite a bit. While not trivial, it's also not that complex to make this work.
