Re: Relation extension scalability

* Amit Langote (Langote_Amit_f8@lab.ntt.co.jp) wrote:
> On 02-04-2015 AM 09:24, Jim Nasby wrote:
> > The other potential advantage (and I have to think this could be a BIG
> > advantage) is extending by a large amount makes it more likely you'll get
> > contiguous blocks on the storage. That's going to make a big difference for
> > SeqScan speed. It'd be interesting if someone with access to some real systems
> > could test that. In particular, seqscan of a possibly fragmented table vs one
> > of the same size but created at once. For extra credit, compare to dd bs=8192
> > of a file of the same size as the overall table.
>
> Orthogonal to topic of the thread but this comment made me recall a proposal
> couple years ago[0] to add (posix_)fallocate to mdextend(). Wonder if it helps
> the case?

As I recall, it didn't, and further, modern filesystems are pretty good
about avoiding fragmentation anyway..

I'm not saying Jim's completely off-base with this idea, I'm just not
sure that it'll really buy us much.
Thanks,
    Stephen