Re: how to build a database from scratch

On 2006-12-08, vc wrote:

>> I meant to say "ordered 2PL" or "2PL like that".
>
> What is "ordered 2PL"?

The thing that was being described. I don't know its True Name. Since all that was specified was that strict 2PL is used, locking was at table granularity, and tables were ordered for update, I took it to mean a scheme intermediate between conservative 2PL where all locks are acquired in advance and held to termination (in order or not in order, we don't care) and strict 2PL (incremental acquisition in any order and release of write locks at termination), which acquires as it goes and releases read locks early, but does so in a global order at table granularity and rolls back all changes after the first acquisition failure. Such a scheme seems intuitively reasonable because it will tend to lead to roundrobin updates and with it static analysis can be used to arrive at a conservative lower bound for the lock set without causing the policy to ever exclusively lock anything that the transaction isn't about to modify.

-- 
Sampo Syreeni, aka decoy - mailto:decoy_at_iki.fi, tel:+358-50-5756111
student/math+cs/helsinki university, http://www.iki.fi/~decoy/front
openpgp: 050985C2/025E D175 ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2