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 >
