Re: how to build a database from scratch

paul c wrote:
> I knew one advanced product, eg., it had a predicate lock
> manager long before any of the big-name dbms'es, that was designed to
> eliminate dba's. Sales were abysmal, in part because dba's in big
> corporations saw this as a big threat and did every thing they could to
> keep the product out.

Or, as is far more likely, your DBAs recognized that predicate locking schemes - which have a 30 years history of commercial and technical failure - simply cannot be used to enforce serializability over the following pair of queries.

Q1:

UPDATE Foo F

    FROM Bar B

       SET F.Val = 5
 WHERE B.X = :VALUE
      AND F.Y = B.Y; Q2:

SELECT * FROM Foo F WHERE F.Y = 5;

If you believe that you can, please explain how you can determine whether the predicates "F.Y = 5" and "F.Y = B.Y" collide? Which is why none of the big-name DBMSs use predicate based locking.

But so what? None of this has anything to do with how to implement B-Trees. Please keep to the topic. Received on Fri Dec 08 2006 - 17:28:37 CST