On Tue, 2008-02-05 at 14:43 +0000, Richard Huxton wrote:
> Simon Riggs wrote:
> > On Tue, 2008-02-05 at 15:06 +0100, Dimitri Fontaine wrote:
> >>
> >> Le lundi 04 février 2008, Jignesh K. Shah a écrit :
>
> >>> Multiple table loads ( 1 per table) spawned via script is bit better
> >>> but hits wal problems.
> >> pgloader will too hit the WAL problem, but it still may have its benefits, or
> >> at least we will soon (you can already if you take it from CVS) be able to
> >> measure if the parallel loading at the client side is a good idea perf. wise.
> >
> > Should be able to reduce lock contention, but not overall WAL volume.
>
> In the case of a bulk upload to an empty table (or partition?) could you
> not optimise the WAL away? That is, shouldn't the WAL basically be a
> simple transformation of the on-disk blocks? You'd have to explicitly
> sync the file(s) for the table/indexes of course, and you'd need some
> work-around for WAL shipping, but it might be worth it for you chaps
> with large imports.
Only by locking the table, which serializes access, which then slows you
down or at least restricts other options. Plus if you use pg_loader then
you'll find only the first few rows optimized and all the rest not.
--
Simon Riggs
2ndQuadrant http://www.2ndQuadrant.com