Anthony W. Youngman kirjutas P, 19.10.2003 kell 21:24: > > As soon as a requirement for a database specifies extraction of the > maximum power from the box, it OUGHT to rule out all the current > relational databases. MV flattens it for it for performance. As an MV > programmer, I *KNOW* that I can find any thing I'm looking for (or find > out it doesn't exist) with just ONE disk seek.
Relational or not, this requires either in-memory index or perfect hash. BTW, how do you find the oldest red elephant "with just one disk seek"? as in SQL: select from elephants where colour=red order by age desc limit 1; > A relational programmer > has to ask the db "does this exist" and hope the db is optimised to be > able to return the result quickly. To quote the Pick FAQ "SQL optimises > the easy task of finding stuff in memory. Pick optimises the hard task > of getting it into memory in the first place". SQL by itself optimises nothing: by definition it evaluates full cross products and then compares all rows with predicates. Some SQL implementations do optimse a little ;) > "Relational" is all about theory and proving things mathematically > correct. "MV" is all about engineering and getting the result. Or perhaps just getting _the_ result ;) getting some other result will probably need another MV database ;) > Unless you can use set theory to predict the future, Isn't this what PostgreSQL's optimiser does ? -------------- Hannu ---------------------------(end of broadcast)--------------------------- TIP 2: you can get off all lists at once with the unregister command (send "unregister YourEmailAddressHere" to [EMAIL PROTECTED])