On Tue, Nov 5, 2013 at 12:25 AM, Leonardo Francalanci <m_li...@yahoo.it>wrote:
> Andres Freund-3 wrote > > On 2013-11-04 11:27:33 -0500, Robert Haas wrote: > >> On Mon, Nov 4, 2013 at 11:24 AM, Claudio Freire < > > > klaussfreire@ > > > > wrote: > >> > Such a thing would help COPY, so maybe it's worth a look > >> > >> I have little doubt that a deferred insertion buffer of some kind > >> could help performance on some workloads, though I suspect the buffer > >> would have to be pretty big to make it worthwhile on a big COPY that > >> generates mostly-random insertions. > > > > Even for random data presorting the to-be-inserted data appropriately > > could result in much better io patterns. > > Mmh, I'm afraid that the buffer should be huge to get some real advantage. > You have to buffer enough values to avoid "touching" entire pages, which is > not that easy. Some experiments I did a few years ago showed that applying sorts to the data to be inserted could be helpful even when the sort batch size was as small as one tuple per 5 pages of existing index. Maybe even less. Cheers, Jeff
