On Mon, Mar 5, 2012 at 12:17 PM, Pavel Stehule <pavel.steh...@gmail.com> wrote: > Hello > > 2012/3/5 Alvaro Herrera <alvhe...@commandprompt.com>: >> >> Excerpts from Artur Litwinowicz's message of lun mar 05 16:18:56 -0300 2012: >>> Dear Developers, >>> I am looking for elegant and effective way for running jobs inside a >>> database or cluster - for now I can not find that solution. >> >> Yeah, it'd be good to have something. Many people say it's not >> necessary, and probably some hackers would oppose it; but mainly I think >> we just haven't agreed (or even discussed) what the design of such a >> scheduler would look like. For example, do we want it to be able to >> just connect and run queries and stuff, or do we want something more >> elaborate able to start programs such as running pg_dump? What if the >> program crashes -- should it cause the server to restart? And so on. >> It's not a trivial problem. >> > > I agree - it is not simple > > * workflow support > * dependency support > > a general ACID scheduler can be nice (in pg) but it is not really > simple. There was some proposal about using autovacuum demon like > scheduler.
I've been thinking about making autovacuum a special case of a general *non*-transactional job-running system because dealing with large physical changes to a database (where one wants to rewrite 300GB of data, or whatever) that are prohibitive in a transaction are -- to understate things -- incredibly painful. Painful enough that people will risk taking their site down with a large UPDATE or ALTER TABLE, hoping that they can survive the duration (and then when they cancel it and are left with huge volumes of dead tuples, things get a lot more ugly). The closest approximation a client program can make is "well, I guess I'll paginate through the database and rewrite small chunks". Instead, it may make more sense to have the database spoon-feed work to do the transformations little-at-a-time ala autovacuum. -- fdr -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
