Optimising MySQL queries against huge databases?

Jasper Bryant-Greene

I have a database of movie titles, with about 78,000 records, and a
database of related people (directors, writers, actors/actresses etc.)
with about 141,000 records. I display a random movie out of this
database on each hit to my website's homepage.

This worked fine when I had only a couple thousand movies, but now that
the DB has grown, it seems to be taking a bit longer to process the
page.

My DB schema for each table:

CREATE TABLE `movies` (
`id` int(11) NOT NULL auto_increment,
`name` varchar(200) NOT NULL default '',
`uri` varchar(100) NOT NULL default '',
`year` year(4) NOT NULL default '0000',
`released` date NOT NULL default '0000-00-00',
`imdb` int(11) NOT NULL default '0',
`allmovies` varchar(25) NOT NULL default '',
`length` int(11) NOT NULL default '0',
`colour` enum('c','b') NOT NULL default 'c',
`sound` varchar(25) NOT NULL default '',
`director` int(11) NOT NULL default '0',
`writer` int(11) NOT NULL default '0',
`asin` varchar(25) NOT NULL default '',
`image` blob NOT NULL,
`genre` varchar(25) NOT NULL default '',
`fatso` int(11) NOT NULL default '0',
PRIMARY KEY (`id`),
UNIQUE KEY `imdb` (`imdb`),
KEY `name` (`name`),
FULLTEXT KEY `name_2` (`name`)
) TYPE=MyISAM AUTO_INCREMENT=78483 ;

CREATE TABLE `people` (
`id` int(11) NOT NULL auto_increment,
`name` varchar(100) NOT NULL default '',
`born` date NOT NULL default '0000-00-00',
`died` date NOT NULL default '0000-00-00',
`imdb` int(11) NOT NULL default '0',
`allmusic` varchar(25) NOT NULL default '',
`allmovies` varchar(25) NOT NULL default '',
`uri` varchar(100) NOT NULL default '',
`image` blob NOT NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `imdb` (`imdb`),
KEY `name` (`name`),
FULLTEXT KEY `name_2` (`name`)
) TYPE=MyISAM AUTO_INCREMENT=141623 ;

The SQL query I am using to fetch a random movie is:

SELECT movies.id, movies.name, movies.asin, movies.fatso, people.id AS
directorid, people.name AS director
FROM movies, people
WHERE movies.image<>'' AND people.id=movies.director
ORDER BY RAND() LIMIT 1;

Jul 17 '05 #1

Michael Vilain

In article <11*********************@z14g2000cwz.googlegroups. com>,
"Jasper Bryant-Greene" <ja******@gmail.com> wrote:

I have a database of movie titles, with about 78,000 records, and a
database of related people (directors, writers, actors/actresses etc.)
with about 141,000 records. I display a random movie out of this
database on each hit to my website's homepage.

This worked fine when I had only a couple thousand movies, but now that
the DB has grown, it seems to be taking a bit longer to process the
page.

My DB schema for each table:

CREATE TABLE `movies` (
`id` int(11) NOT NULL auto_increment,
`name` varchar(200) NOT NULL default '',
`uri` varchar(100) NOT NULL default '',
`year` year(4) NOT NULL default '0000',
`released` date NOT NULL default '0000-00-00',
`imdb` int(11) NOT NULL default '0',
`allmovies` varchar(25) NOT NULL default '',
`length` int(11) NOT NULL default '0',
`colour` enum('c','b') NOT NULL default 'c',
`sound` varchar(25) NOT NULL default '',
`director` int(11) NOT NULL default '0',
`writer` int(11) NOT NULL default '0',
`asin` varchar(25) NOT NULL default '',
`image` blob NOT NULL,
`genre` varchar(25) NOT NULL default '',
`fatso` int(11) NOT NULL default '0',
PRIMARY KEY (`id`),
UNIQUE KEY `imdb` (`imdb`),
KEY `name` (`name`),
FULLTEXT KEY `name_2` (`name`)
) TYPE=MyISAM AUTO_INCREMENT=78483 ;

CREATE TABLE `people` (
`id` int(11) NOT NULL auto_increment,
`name` varchar(100) NOT NULL default '',
`born` date NOT NULL default '0000-00-00',
`died` date NOT NULL default '0000-00-00',
`imdb` int(11) NOT NULL default '0',
`allmusic` varchar(25) NOT NULL default '',
`allmovies` varchar(25) NOT NULL default '',
`uri` varchar(100) NOT NULL default '',
`image` blob NOT NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `imdb` (`imdb`),
KEY `name` (`name`),
FULLTEXT KEY `name_2` (`name`)
) TYPE=MyISAM AUTO_INCREMENT=141623 ;

The SQL query I am using to fetch a random movie is:

SELECT movies.id, movies.name, movies.asin, movies.fatso, people.id AS
directorid, people.name AS director
FROM movies, people
WHERE movies.image<>'' AND people.id=movies.director
ORDER BY RAND() LIMIT 1;

what does the EXPLAIN <query> tell you? It should show the strategy
used by optimizer. You may have to do some rephrasing. Have you posted
this in a mysql group:

http://groups-beta.google.com/group/alt.php.sql
http://groups-beta.google.com/group/...database.mysql

--
DeeDee, don't press that button! DeeDee! NO! Dee...

Jul 17 '05 #2

Henk Verhoeven

Hi Jasper,

I agree with Michael about the explain, but i did not try that, so the
following are just guesses:
- there is no index on movies.image so mySQL must sequentially search
throuhg all movies that have a director (probably all or close to all 141000
- there are probably MANY movies that have an image and a director.
Unless MySQL has a special optimization for ORDER BY RAND() LIMIT ..
it may have to random-sort all of them. That will take quite some time,
i guess. So if an index on movies.image does not help, you may have to
add AND id = RAND() to the SELECT condition, with the RAND function
parameterized or multiplied and rounded or floored to get whole numbers
between the lowest and highest id in the database. And then repeat the
query until it does return a row. (if many rows have been removed you
may have to pack the id's of movies)

Success,

Henk Verhoeven,
www.phpPeanuts.org.

Jul 17 '05 #3