On Tue, Nov 5, 2013 at 12:25 AM, Leonardo Francalanci <m_lists@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.
