On 06/19/2011 09:38 AM, Greg Stark wrote:
There's another problem which I haven't seen mentioned. Because the access method will affect the cache there's the possibility of feedback loops. e.g. A freshly loaded system prefers sequential scans for a given table because without the cache the seeks of random reads are too expensive...
Not sure if it's been mentioned in this thread yet, but he feedback issue has popped up in regards to this area plenty of times. I think everyone who's producing regular input into this is aware of it, even if it's not mentioned regularly. I'm not too concerned about the specific case you warned about because I don't see how sequential scan vs. index costing will be any different on a fresh system than it is now. But there are plenty of cases like it to be mapped out here, and many are not solvable--they're just something that needs to be documented as a risk.
-- Greg Smith 2ndQuadrant US g...@2ndquadrant.com Baltimore, MD PostgreSQL Training, Services, and 24x7 Support www.2ndQuadrant.us -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
