On Mar 7, 2007, at 4:00 PM, Alvaro Herrera wrote:
Is everybody OK with putting per-database worker limits on a pg_database

I'm worried that we would live to regret such a limit. I can't really see any reason to limit how many vacuums are occurring in a database, because there's no limiting factor there; you're either going to be IO bound (per-tablespace), or *maybe* CPU-bound (perhaps the Greenplum folks could enlighten us as to whether they run into vacuum being CPU-bound on thumpers).

Changing the naptime behavior to be database related makes perfect sense, because the minimum XID you have to worry about is a per- database thing; I just don't see limiting the number of vacuums as being per-database, though. I'm also skeptical that we'll be able to come up with a good way to limit the number of backends until we get the hot table issue addressed. Perhaps a decent compromise for now would be to limit how many 'small table' vacuums could run on each tablespace, and then limit how many 'unlimited table size' vacuums could run on each tablespace, where 'small table' would probably have to be configurable. I don't think it's the best final solution, but it should at least solve the immediate need.
Jim Nasby                                            [EMAIL PROTECTED]
EnterpriseDB      http://enterprisedb.com      512.569.9461 (cell)

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