The osdl-dbt3 test starts with building and vacuuming the database. The execution plans were taken after the vacuuming.
I did two tests with the same database parameters: 1. run two osdl-dbt3 runs on one box without rebooting the stystem. Though the execution plans are the same, the costs are different. The system status are different for the two runs, for example, some page cache are not released after the first one. Does that make the cost different? 2. run two osdl-dbt3 runs on two boxes. The hardware of the two boxes are the same. And each run starts from scratch (building linux kernel, pgsql ect, and reboot). To my surprise, not only the cost are different between the two runs, the execution plan changed for Query 9. The execution plans can be found at: http://khack.osdl.org/stp/277780/results/plan/power_query9.txt http://khack.osdl.org/stp/277779/results/plan/power_query9.txt My test leads me to the following questions: What are the factors which determine the execution plan and cost? Does PostgreSQL check the system resource dynamically? If Inserts and Updates happened but vacuuming is not executed, dose the execution plan change? Thanks, -- Jenny Zhang Open Source Development Lab Inc 12725 SW Millikan Way Suite 400 Beaverton, OR 97005 (503)626-2455 ext 31 ---------------------------(end of broadcast)--------------------------- TIP 2: you can get off all lists at once with the unregister command (send "unregister YourEmailAddressHere" to [EMAIL PROTECTED])
