no one have any explanation ? what i don't understand is that in select IDObj From DESCRIPTION where ID='ID_NOT_EXIST' the speed is slow when no record are founded (so the number of field/size in table Description must not matter, only the size of the index) ! but it's not the case, i do several test to confirm it ....
so it's mean that the data of the index is stored INSIDE the page of the reccord ?? --- In [email protected], "nathanelrick" <nathanelrick@...> wrote: > > Dear Mark, > > > Quite simple: with a field of VARCHAR(10000) on 8K pages it needs to read > > at least two pages if the VARCHAR is filled for over 80%, for smaller > > VARCHARs there is still a relatively high chance it will need to read 2 > > pages. For page sizes of 16K this is less, but still relatively high > > (especially if the field is filled for a large percentage). If there are > > multiple record versions that need to be processed even more pages need to > > be read. Reading more pages => more IO => more time. > > > YEs this i understand, but what i don't understand is that in my select > (select IDObj From DESCRIPTION where ID='ID_NOT_EXIST') the speed is the same > ! :( here normally no data page must be read (because no row was found), only > page used by the index must be read ? > > I also try with blob, unfortunatly nothing change, just a little little > (around 10%) more faster with blob :( > > > > > > > > BTW: Try to use BLOBs instead of VARCHAR(10000), it might reduces this > > problem > > > > Mark > > >
