	There is one comment I would like to state, on the issue of 
	a sequential scan beeing faster than an index scan. It is actually
often
	true in a singel user system that an index scan is more expensive
	than a sequential scan. 
	As long as we have table level locks this is also true for heavyly
	concurrent access.
	Here comes the disadvantage:
	Once row or page locks will be implemented, the sequential scan
	cost should be reconsidered, since then readers will often be
waiting 
	for updaters, that are actually updating data, that is irrelevant
for the
	reader. The average wait time will have to be added to the sequ.
scan
	cost.

	Andreas

Mon, 30 Mar 1998 14:20:42 +0200
Zeugswetter Andreas SARZ <Andreas.Zeugswetter@telecom.at>
AW: [HACKERS] Optimizer fails?