On Tue, 2008-12-23 at 10:10 -0600, Kevin Grittner wrote: > Well, I figured I should try to get a consensus here before submitting > a patch. Last time I tried submitting a simple patch to remove the > line about the PostgreSQL community not knowing about any other > databases which use predicate locking, I got shot down hard.
The docs got changed though. I think the current docs make too much of a deal about how hard it is to do predicate locking in databases. Most RDBMS use predicate locking via indexes, ie the locking happens in the index. One might also argue that it is potentially more efficient design, as TPC-C shows, though such cases of application scalability are rare in the extreme and the utility of MVCC is by far the best general approach in terms of ease of use and performance. The example in the docs is not a realistic example, so your new one is useful. I would want you to update it though to show how use of row level locks can be used to enforce correct behaviour when required, so provide a problem and its solution. It will b useful for people moving from systems like Sybase that use locking often fall foul of the *lack* of locking in MVCC and write programs that won't work correctly as a result. -- Simon Riggs www.2ndQuadrant.com PostgreSQL Training, Services and Support -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
