Hey all,

I've heard through the grapevine that a varchar is not an appropriate
data type for a column that is a key column, or one that is heavily joined
on. Can anyone out there give me a definitive answer as to whether or not
there any performance issue(s) to be concerned with here?

thanks for your help!
Grant

"Grant Wolcott" <wolcott (AT) fstrf (DOT) org> wrote

That is pretty close to being a superstition. However there are internal
limits to the size of a key attribute, and it is easy enough to define a
varchar that exceeds it (400 bytes). Large keys can--in principle-slightly
impair performance, but I have yet to see a real system where there weren't
also a host of other WAY worse problems that completely swamp any small
performance penalty that large keys incur.

Varchars as keys were historically more of a problem than they are today.
It rather depends on how big you intend the attribute to be. Luckly, in
nature, one rarely sees truly enormous keys. (Directory paths are one
notorious exception that springs to mind though.)

Varchars per se are perfectly OK as key attributes--as they necessarily must
be if Ingres wants to be called an RDBMS.

Roy Hann (rhann at rationalcommerce dot com)
Rational Commerce Ltd.
www.rationalcommerce.com
"Ingres development, tuning, and training experts"

At 4:17 PM +0000 3/18/05, Roy Hann wrote:
Oh boy. It's Friday and Roy is starting to talk about what it
takes to be called an RDBMS. MySQL lovers beware ...

;-)

--
Michael Leo Java, J2EE, BEA WebLogic,
Caribou Lake LLC Oracle, Open Source, Ingres,
mleo (AT) cariboulake (DOT) com Real Enterprise Applications

Climate is what we expect. Weather is what we get.
- Mark Twain

Thanks lots, Roy - this gives me more confidence to barrel ahead... We
want to change some of the columns of our in-house dictionary tables from
char(8) to varchar(32). Obviously, these tables are heavily used and often
joined w/other tables - so you can see our concerns.

thanks again,
Grant


At 04:17 PM 3/18/2005 +0000, Roy Hann wrote:

"Grant Wolcott" <wolcott (AT) fstrf (DOT) org> wrote

That'll be fine. (And besides, what's the alternative?)

Roy