Re: Index on columns that have total of more than 255

Jack Parker wrote: > > Forgive my pointing this out, but a 255 long index defeats the purpose of > indexing. The concept is to have a small copy of the table with just some > primary identifier that you can check against - if that turns out to be 255 > then you wind up getting four whole indexes per 1K page (ok 8 for some of > us and 16 for others) - before you count in the overhead. At that point it > is going to be about just as fast to read the table sequentially as it will > be to do a btree based on a key that long. I don't know what the > application is, but you should reconsider the model it is based on if it > requires keys that long. > > As to why you can't? Everybody has limits - it would appear as though ours > are too low in this case. Generally I start screaming at the modeller when Or someone else's are too long? Ian