query-optimization

I've written a little app that parses expressions into abstract syntax trees. Right now, I use a bunch of heuristics against the expression in order to decide how to best evaluate the query. Unfortunately, there are examples which make the query plan extremely bad. I've found a way to provably make better guesses as to how queries should be evaluated, but I need to put my expression into CNF or DNF first in order to get provably correct answers. I know this could result in potentially exponential time and space, but for typical queries my users run this is not a problem. Now, converting to CNF

I have a fairly stable directed graph of order ~100k vertices and size ~1k edges. It is two-dimensional insofar as its vertices can be identified by a pair of integers (x, y) (of cardinality ~100 x ~1000) and all edges are strictly increasing in x . There is furthermore a dictionary of ~1k (key, val) pairs associated with each vertex. I am currently storing the graph in a MySQL database across three (InnoDB) tables: a table of vertices (which I don't think is relevant to my question, so I have omitted to include both it and the foreign key constraints that refer to it in my extracts below); a

Is there a way to optimize this further or should I just be satisfied that it takes 9 seconds to count 11M rows ? devuser@xcmst > mysql --user=user --password=pass -D marctoxctransformation -e "desc record_updates" +--------------+----------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +--------------+----------+------+-----+---------+-------+ | record_id | int(11) | YES | MUL | NULL | | | date_updated | datetime | YES | MUL | NULL | | +--------------+----------+------+-----+---------+-------+ devuser@xcmst > date; mysql --user=user --password=pass -D

I have two tables: CREATE TABLE `articles` ( `id` int(11) NOT NULL AUTO_INCREMENT, `title` varchar(1000) DEFAULT NULL, `last_updated` datetime DEFAULT NULL, PRIMARY KEY (`id`), KEY `last_updated` (`last_updated`), ) ENGINE=InnoDB AUTO_INCREMENT=799681 DEFAULT CHARSET=utf8 CREATE TABLE `article_categories` ( `article_id` int(11) NOT NULL DEFAULT '0', `category_id` int(11) NOT NULL DEFAULT '0', PRIMARY KEY (`article_id`,`category_id`), KEY `category_id` (`category_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 | This is my query: SELECT a.* FROM articles AS a, article_categories AS c WHERE a.id = c

The usual case. I have a simple app that will allow people to upload photos and follow other people. As a result, every user will have something like a "wall" or an "activity feed" where he or she sees the latest photos uploaded from his/her friends (people he or she follows). Most of the functionalities are easy to implement. However, when it comes to this history activity feed, things can easily turn into a mess because of pure performance reasons. I have come to the following dilemma here: i can easily design the activity feed as a normalized part of the database, which will save me writing