persistentstorage/dbms/group/TODO.TXT
author Chris Dudding <chris.dudding@nokia.com>
Tue, 13 Jul 2010 18:32:07 +0100
changeset 37 5ce4638b3d6d
parent 0 08ec8eefde2f
permissions -rw-r--r--
DEADHEAD Closing redundant branch: Bug 3168 (changeset 32: 0bacd7dbb9a9) is already incorporated in the 201025_05 bulk delivery (changeset 33: 5e4beccba4e9).

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