On 8/7/07, Decibel! <[EMAIL PROTECTED]> wrote: > On Tue, Aug 07, 2007 at 02:33:19PM +0100, Richard Huxton wrote: > > Mark Makarowsky wrote: > > >I have a table with 4,889,820 records in it. The > > >table also has 47 fields. I'm having problems with > > >update performance. Just as a test, I issued the > > >following update: > > > > > >update valley set test='this is a test' > > > > > >This took 905641 ms. Isn't that kind of slow? > > > > The limiting factor here will be how fast you can write to your disk. > > Well, very possibly how fast you can read, too. Using your assumption of > 1k per row, 5M rows means 5G of data, which might well not fit in > memory. And if the entire table's been updated just once before, even > with vacuuming you're now at 10G of data.
Where one might have to update just one column of a wide table often, it's often a good idea to move that column into its own dependent table. Or just don't update one column of every row in table... ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings
