persistentstorage/dbms/group/TODO.TXT
author Dremov Kirill (Nokia-D-MSW/Tampere) <kirill.dremov@nokia.com>
Fri, 22 Jan 2010 11:06:30 +0200
changeset 0 08ec8eefde2f
permissions -rw-r--r--
Revision: 201003 Kit: 201003

Things that could be done to DBMS -- 12 October 1998

Query optimizer:

	Optimize for clustering indexes (use S/T and G/H plans)
		e.g. assume Auto-increment column => clustering
		or measure the clustering in the stats

	Optimize for multi-column lookup
		e.g. For "a=v1 and b=v2" with index on (a,b)

	Optimize for like-predicates
		e.g. "x LIKE 'abc*'" => "x>='abc' AND x<'abd'" etc.

	Query complexity-reduction by removing redundant predicates, e.g.
		"x>4 AND x>3" => "x>4"
		"x>4 OR x>3" => "x>3"
		"x>-1" for unsigned x => trivially true

	Better statistical data dn guesswork

SQL/access plans:
	
	Support "DISTINCT" in the projection stage via a Hash-system or sorting